Microbolometer systems and methods

ABSTRACT

Microbolometer systems and methods are provided herein. For example, an infrared imaging device includes a microbolometer array. The microbolometer array includes a plurality of microbolometers. Each microbolometer includes a microbolometer bridge that includes a first portion and a second portion. The first portion includes a resistive layer configured to capture infrared radiation. The second portion includes a second portion having a plurality of perforations defined therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2020/022195 filed Mar. 11, 2020 entitled “MICROBOLOMETERSYSTEMS AND METHODS,” which is incorporated herein by reference in itsentirety.

International Patent Application No. PCT/US2020/022195 claims priorityto and the benefit of U.S. Provisional Patent Application No. 62/816,889filed on Mar. 11, 2019 and entitled “VERTICAL MICROBOLOMETER CONTACTSYSTEMS AND METHODS,” which is hereby incorporated by reference in itsentirety.

International Patent Application No. PCT/US2020/022195 claims priorityto and the benefit of U.S. Provisional Patent Application No. 62/907,548filed on Sep. 27, 2019 and entitled “MICROBOLOMETER SYSTEMS ANDMETHODS,” which is hereby incorporated by reference in its entirety.

International Patent Application No. PCT/US2020/022195 claims priorityto and the benefit of U.S. Provisional Patent Application No. 62/907,555filed on Sep. 28, 2019 and entitled “MICROBOLOMETER SYSTEMS ANDMETHODS,” which is hereby incorporated by reference in its entirety.

International Patent Application No. PCT/US2020/022195 is related toU.S. patent application Ser. No. 16/226,580 filed Dec. 19, 2018 andentitled “VERTICAL MICROBOLOMETER CONTACT SYSTEMS AND METHODS,” which inturn is a divisional of U.S. patent application Ser. No. 15/396,100filed Dec. 30, 2016 and entitled “VERTICAL MICROBOLOMETER CONTACTSYSTEMS AND METHODS,” which in turn is a continuation of InternationalPatent Application No. PCT/US2015/039138 filed Jul. 2, 2015 and entitled“VERTICAL MICROBOLOMETER CONTACT SYSTEMS AND METHODS,” which in turnclaims priority to and the benefit of U.S. Provisional PatentApplication No. 62/020,747 filed on Jul. 3, 2014 and entitled “VERTICALMICROBOLOMETER CONTACT SYSTEMS AND METHODS,” the contents all of whichare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

One or more embodiments of the invention relate generally to infraredcameras and, more particularly, to microbolometer contact systems andmethods, such as vertical leg contacts for microbolometer focal planearrays.

BACKGROUND

A microbolometer is an example of a type of infrared detector that maybe used within an infrared imaging device (e.g., an infrared camera).For example, the microbolometer is typically fabricated on a monolithicsilicon substrate to form an infrared (image) detector array, with eachmicrobolometer of the infrared detector array functioning as a pixel toproduce a two-dimensional image. The change in resistance of eachmicrobolometer is translated into a time-multiplexed electrical signalby circuity known as the read out integrated circuit (ROIC). Thecombination of the ROIC and the infrared detector array (e.g.,microbolometer array) is commonly known as a focal plane array (FPA) orinfrared FPA (IRFPA). Additional details regarding FPAs andmicrobolometers may be found, for example, in U.S. Pat. Nos. 5,756,999,6,028,309, 6,812,465, and 7,034,301, which are herein incorporated byreference in their entirety.

Each microbolometer in the array is generally coupled to one or morecontacts that extend vertically from the array down to the ROIC. Thecontacts can be used for providing a reference voltage for themicrobolometer and/or a signal path from the microbolometer to the ROIC.Microbolometers often include a light-sensitive portion formed fromresistive material suspended on a bridge, with the resistive materialcoupled to its contacts via legs that run from the bridge to thecontacts. The legs attach to resistive material through a resistivematerial contact.

One of the challenges in designing efficient microbolometers isincreasing the ratio of the light-sensitive area or the active pixelarea to the total area of the array, sometimes referred to as the fillfactor of the array. Leg supports for each microbolometer can occupy asignificant portion of the array area and can therefore limit the fillfactor of the array. It would therefore be desirable to reduce theamount of area occupied by the legs. However, in order to maintaindevice performance, the width and length of each leg support shouldscale with the area of each pixel. It can therefore be difficult toreduce the leg area and increase the fill factor. As a result, there isa need for improved techniques for implementing leg supports, such asfor microbolometer-based focal plane arrays.

SUMMARY

Systems and methods are disclosed, in accordance with one or moreembodiments, which are directed to microbolometer legs for an infrareddetector. For example, in accordance with an embodiment of theinvention, vertical legs are disclosed, such as for infrared detectorswithin a focal plane array, that may be more area efficient as comparedto conventional legs that extend horizontally substantially in planewith the infrared detector. For one or more embodiments, the leg systemsand methods disclosed herein may provide certain advantages overconventional leg approaches, especially as semiconductor processingtechnologies transition to smaller dimensions.

In accordance with one embodiment, an infrared imaging device includes asubstrate including a plurality of contacts and a surface. The surfacedefines a plane. The infrared imaging device further includes amicrobolometer array coupled to the substrate, where the microbolometerarray includes a plurality of microbolometers. Each microbolometerincludes a bridge and a leg structure coupled to the bridge and to oneof the plurality of contacts. The leg structure includes a metal layerhaving a first dimension that extends in a first direction that issubstantially perpendicular to the plane and a second dimension thatextends in a second direction that is substantially parallel to theplane, where the first dimension is greater than the second dimension.The leg structure further includes a first layer formed on a firstsidewall of the metal layer and a first side of the metal layer. The legstructure further includes a second layer formed on a second sidewall ofthe metal layer and a second side of the metal layer. The first sidewallis opposite the second sidewall. The first side is opposite the secondside.

In accordance with one embodiment, an infrared imaging device includes amicrobolometer array including a plurality of microbolometers. Eachmicrobolometer includes a bridge. The bridge includes a first portioncomprising a resistive layer configured to capture infrared radiationand a second portion having a plurality of perforations defined therein.

In accordance with one embodiment, an infrared imaging device includesan array of microbolometers each having a bridge that is coupled to acontact by at least one vertical bolometer leg. The legs and bridges ofthe microbolometer array may be suspended above a readout integratedcircuit for the microbolometer array. The vertical bolometer legs may beformed using spacer deposition and etch processing operations that format least portions of the vertical bolometer legs on the sidewalls of anopening in a sacrificial layer that is then removed to release thebolometer legs.

According to various embodiments, a vertical bolometer leg may run alonga path that is disposed in a plane that is parallel to a plane definedby the bridge of the microbolometer and/or a plane that is defined by asurface of a substrate of the device such as a readout integratedcircuit substrate and may have an extended dimension that extends in adirection that is perpendicular to the plane of the path, the substratesurface, and/or the plane of the bridge. In this way, the area of thebolometer leg that would otherwise occupy a relatively larger fractionof the surface area of the microbolometer array can be reduced withoutreducing the area of the bolometer leg.

According to various embodiments, the leg structure may or may not beencapsulated in an insulating layer such as a silicon dioxide or asilicon nitride. The leg structure may be formed from multiple layers ofinsulating material to optimize performance. A leg conductive layer maybe fully or partially encapsulated with an insulation layer, or may befree of any insulation layer. The leg conductive layer may be ahomogeneous film of a single material type or a multilayer conductivelayer formed from, for example, several depositions.

In accordance with one embodiment, an infrared imaging device includes asubstrate having a plurality of contacts and a surface. The surfacedefines a plane. The infrared imaging device further includes amicrobolometer array coupled to the substrate, where the microbolometerarray includes a plurality of microbolometers. Each microbolometerincludes a bridge and a leg structure coupled to the bridge and to oneof the plurality of contacts. The leg structure includes a cross-sectionhaving a first section, a second section substantially parallel to thefirst section, and a third section joining the first section and thesecond section. In some aspects, the bridge has a first portion and asecond portion. The first portion includes a resistive layer configuredto capture infrared radiation. The second portion includes a pluralityof perforations defined therein.

In accordance with one embodiment, a method of forming an infraredimaging device includes forming a bridge on a sacrificial layer. Themethod further includes forming an opening in the sacrificial layer. Themethod further includes disposing a contact metal layer on sidewalls ofthe opening. The method further includes forming a leg structure thatcouples to the bridge and the contact metal layer. The leg structure hasa cross-section having a first section, a second section substantiallyparallel to the first section, and a third section joining the firstsection and the second section. The method further includes removing thesacrificial layer to suspend the bridge and the leg structure above asubstrate of the infrared imaging device. The contact metal layer iscoupled to the substrate.

In accordance with one embodiment, an infrared imaging device includes amicrobolometer array having a plurality of microbolometers. Eachmicrobolometer includes a microbolometer bridge. The microbolometerbridge includes a first portion comprising a resistive layer configuredto capture infrared radiation; and a second portion having a pluralityof perforations defined therein. In some aspects, the infrared imagingdevice further includes a substrate including a plurality of contactsand a surface. The surface defines a plane. Each microbolometer furtherincludes a leg structure coupled to the microbolometer bridge and to oneof the plurality of contacts. The leg structure includes a cross-sectionhaving a first section, a second section substantially parallel to thefirst section, and a third section joining the first section and thesecond section.

In accordance with one embodiment, a method of forming an infraredimaging device includes forming a bridge structure. The method furtherincludes forming a leg structure. The method further includes formingthe plurality of perforations in the bridge structure to obtain amicrobolometer bridge.

In accordance with one embodiment, a method of forming an infraredimaging device includes forming a bridge on a sacrificial layer, wherethe bridge includes a first portion having a resistive layer configuredto capture infrared radiation and a second portion having a plurality ofperforations formed therein. The method further includes forming anopening in the sacrificial layer. The method further includes disposinga contact metal layer on sidewalls of the opening. The method furtherincludes forming a leg structure that couples to the bridge and thecontact metal layer. The method further includes removing thesacrificial layer to suspend the bridge and the leg structure above asubstrate of the infrared imaging device, where the contact metal layeris coupled to the substrate.

The scope of the invention is defined by the claims, which areincorporated into this Summary by reference. A more completeunderstanding of embodiments of the invention will be afforded to thoseskilled in the art, as well as a realization of additional advantagesthereof, by a consideration of the following detailed description of oneor more embodiments. Reference will be made to the appended sheets ofdrawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram illustrating an infrared camera inaccordance with one or more embodiments.

FIG. 2 shows a block diagram illustrating an implementation example foran infrared camera in accordance with one or more embodiments.

FIG. 3 shows a physical layout diagram of a microbolometer of amicrobolometer array having vertical legs in accordance with anembodiment.

FIGS. 4A and 4B show a top view and a cross-sectional side viewrespectively of a conventional horizontal leg for a microbolometer.

FIGS. 5A and 5B show a top view and a cross-sectional side viewrespectively of a vertical leg such as for a leg for coupling aninfrared detector element to a contact, in accordance with anembodiment.

FIGS. 6A through 6F illustrate a processing overview for manufacturing avertical leg, such as for the vertical legs of FIG. 3, in accordancewith an embodiment.

FIGS. 7A through 7F illustrate another processing overview formanufacturing a vertical leg, such as for the vertical legs of FIG. 3,in accordance with an embodiment.

FIGS. 8A through 8C illustrate a yet another processing overview formanufacturing a vertical leg, such as for the vertical legs of FIG. 3,in accordance with an embodiment.

FIG. 9 shows a cross-sectional side view, in the vicinity of a verticalcontact between an infrared detector array and a readout integratedcircuit, of a portion of a focal plane array having vertical legs thatare formed below a surface of the array, in accordance with anembodiment.

FIG. 10 shows a cross-sectional side view, in the vicinity of a sensorof the array, of a portion of a focal plane array having vertical legsthat are formed below a surface of the array, in accordance with anembodiment.

FIG. 11 shows a cross-sectional side view, in the vicinity of a verticalcontact between an infrared detector array and a readout integratedcircuit, of a portion of a focal plane array having vertical legs thatare formed below a surface of the array, in accordance with anembodiment.

FIG. 12 shows a cross-sectional side view, in the vicinity of a sensorof the array, of a portion of a focal plane array having vertical legsthat are formed below a surface of the array, in accordance with anembodiment.

FIGS. 13A through 13Q show various arrangements of a vertical leg, suchas for the vertical legs of FIGS. 5A and 5B, in accordance with variousembodiments.

FIG. 14 shows a cross-sectional side view, in the vicinity of a verticalcontact between an infrared detector array and a readout integratedcircuit, of a portion of a focal plane array having vertical legs formedat or above a surface of the array, in accordance with an embodiment.

FIG. 15 shows a cross-sectional side view, in the vicinity of a sensorof the array, of a portion of a focal plane array having vertical legsformed above a surface of the array, in accordance with an embodiment.

FIG. 16 shows a top view of a bend portion of a vertical leg, such asfor the vertical legs of FIG. 3 in the vicinity of a bend in thevertical leg, in accordance with an embodiment.

FIG. 17 shows a cross-sectional view of an example arrangement of thevertical leg of FIG. 16, in accordance with an embodiment.

FIG. 18 shows a cross-sectional view of another example arrangement ofthe vertical leg of FIG. 16, in accordance with an embodiment.

FIG. 19 shows a cross-sectional view of a portion of a focal plane arrayhaving legs, such as legs for an infrared detector, that are formed atleast partially beneath a bridge portion of the infrared detector, inaccordance with an embodiment.

FIG. 20 illustrates a flow diagram for manufacturing a vertical leg,such as for the vertical legs of FIG. 3, in accordance with anembodiment.

FIG. 21 illustrates another flow diagram for manufacturing a verticalleg, such as for the vertical legs of FIG. 3, in accordance with anembodiment.

FIG. 22 illustrates yet another flow diagram for manufacturing avertical leg, such as for the vertical legs of FIG. 3, in accordancewith an embodiment.

FIGS. 23A through 23F illustrate a processing overview for manufacturinga vertical leg, such as for the vertical legs of FIG. 3 using an etchstop layer, in accordance with an embodiment.

FIG. 24 shows a cross-sectional view of a portion of a focal plane arrayhaving legs, such as legs for an infrared detector, that are formed atleast partially beneath a bridge portion of the infrared detector, inaccordance with an embodiment.

FIG. 25 illustrates a flow diagram for manufacturing a focal plane arrayhaving legs, such as legs for an infrared detector, that are formed atleast partially beneath a bridge portion of the infrared detector, inaccordance with an embodiment.

FIG. 26 shows a top-down view of a bolometer.

FIG. 27 shows a cross-section of a leg of the bolometer of FIG. 26.

FIG. 28 shows rigidity provided by a vertical component.

FIG. 29 shows a top-down view of a bolometer having vertical legs inaccordance with an embodiment.

FIG. 30A shows a cross-section of a leg of the bolometer of FIG. 29 inaccordance with an embodiment.

FIG. 30B illustrates a cross-section of a leg having a height smallerthan that of the leg of FIG. 30A, in accordance with an embodiment.

FIG. 31 illustrates a cross-section of a leg of a bolometer inaccordance with an embodiment.

FIG. 32 shows a top-down view of a bolometer having a bridge, verticallegs, and contacts, in which an oxide approach is utilized tomanufacture the bolometer, in accordance with an embodiment.

FIG. 33 shows a cross-section of a leg of FIG. 32 in accordance with anembodiment.

FIG. 34 shows a top-down view of a bolometer having a bridge, verticallegs, and contacts, in which a directed self-assembly approach isutilized to manufacture the bolometer, in accordance with an embodiment.

FIG. 35 shows a cross-section of a leg of FIG. 34 in accordance with anembodiment.

FIGS. 36A through 36N illustrate cross-sectional side views associatedwith an example process for forming a bolometer in accordance with anembodiment.

FIG. 37 illustrate a top-down view corresponding to the cross-sectionalside view of FIG. 36N in accordance with an embodiment.

FIGS. 38A through 38D illustrate cross-sectional side views associatedwith an example process for forming a contact in accordance with anembodiment.

FIGS. 39A through 39D illustrate cross-sectional side views associatedwith an example process for forming legs after a contact to a readoutcircuit wafer has been formed in accordance with an embodiment.

FIG. 39E illustrate a zoomed-in view of a portion of the structure ofFIG. 39D.

FIG. 40 illustrates a top-down view corresponding to the cross-sectionalside view of FIG. 39D in accordance with an embodiment.

FIGS. 41A through 41T illustrate cross-sectional side view associatedwith an example process for forming a bolometer in accordance with anembodiment.

FIG. 42 illustrate top-down views corresponding to the cross-sectionalside views of FIG. 41T in accordance with an embodiment.

FIGS. 43A and 43B illustrate views associated with a bolometer inaccordance with an embodiment.

FIGS. 44A through 44E illustrate various views associated with anotherbolometer in accordance with an embodiment.

FIGS. 45A through 45F illustrate cross-sectional side views associatedwith an example process for forming a bolometer in accordance with anembodiment.

FIGS. 46A through 46F illustrate top-views associated with the exampleprocess of FIGS. 45A through 45F in accordance with an embodiment.

FIGS. 47A and 47B illustrate zoom-in views of portions identified inFIG. 45C.

FIG. 48 is a flowchart of illustrative operations that may be performedfor forming a bolometer according to an embodiment.

FIG. 49 illustrates a perspective view of a bolometer in accordance withan embodiment.

FIG. 50 illustrates a top view of the bolometer of FIG. 49 in accordancewith an embodiment.

FIGS. 51A through 51C illustrate additional examples of bolometers inaccordance with one or more embodiments.

FIG. 52 illustrates a cross-sectional side view of a portion of abolometer in accordance with an embodiment.

FIG. 53 illustrates a cross-section side view of a portion of abolometer having perforations defined therein in accordance with anembodiment.

FIG. 54 is a flowchart of illustrative operations that may be performedfor forming a bolometer having perforations defined in the bolometer'sbridge in accordance with an embodiment.

FIGS. 55A through 55D illustrate cross-sectional side views associatedwith an example process for forming a bolometer in accordance with anembodiment.

FIG. 56 illustrates a top-down view corresponding to the cross-sectionalside view of FIG. 55D in accordance with an embodiment.

Embodiments of the invention and their advantages are best understood byreferring to the detailed description that follows. It should beappreciated that like reference numerals are used to identify likeelements illustrated in one or more of the figures.

DETAILED DESCRIPTION

Systems and methods are disclosed herein to provide vertically orientedlegs for an infrared detector, in accordance with one or moreembodiments. For example, in accordance with an embodiment, verticalbolometer legs are disclosed, such as for microbolometers within a focalplane array. As an implementation example, FIG. 1 shows a block diagramillustrating a system 100 (e.g., an infrared camera, including any typeof infrared imaging system) for capturing images and processing inaccordance with one or more embodiments. System 100 comprises, in oneimplementation, an image capture component 102, a processing component104, a control component 106, a memory component 108, and a displaycomponent 110. Optionally, system 100 may include a sensing component112.

System 100 may represent, for example, an infrared imaging device, suchas an infrared camera, to capture and process images, such as videoimages of a scene 101. The system 100 may represent any type of infraredcamera that employs infrared detectors having contacts, which may beimplemented as disclosed herein. System 100 may comprise a portabledevice and may be incorporated, e.g., into a vehicle (e.g., anautomobile or other type of land-based vehicle, an aircraft, or aspacecraft) or a non-mobile installation requiring infrared images to bestored and/or displayed or may comprise a distributed networked system(e.g., processing component 104 distant from and controlling imagecapture component 102 via the network).

In various embodiments, processing component 104 may comprise any typeof a processor or a logic device (e.g., a programmable logic device(PLD) configured to perform processing functions). Processing component104 may be adapted to interface and communicate with components 102,106, 108, and 110 to perform method and processing steps and/oroperations, such as for example, controlling biasing and other functions(e.g., values for elements such as variable resistors and currentsources, switch settings for biasing and timing, and other parameters)along with other conventional system processing functions as would beunderstood by one skilled in the art.

Memory component 108 comprises, in one embodiment, one or more memorydevices adapted to store data and information, including for exampleinfrared data and information. Memory device 108 may comprise one ormore various types of memory devices including volatile and non-volatilememory devices, including computer-readable medium (portable or fixed).Processing component 104 may be adapted to execute software stored inmemory component 108 so as to perform method and process steps and/oroperations described herein.

Image capture component 102 comprises, in one embodiment, one or moreinfrared sensors (e.g., any type of multi-pixel infrared detector, suchas a focal plane array having one or more vertical legs as disclosedherein) for capturing infrared image data (e.g., still image data and/orvideo data) representative of an image, such as scene 101. In oneimplementation, the infrared sensors of image capture component 102provide for representing (e.g., converting) the captured image data asdigital data (e.g., via an analog-to-digital converter included as partof the infrared sensor or separate from the infrared sensor as part ofsystem 100). In one or more embodiments, image capture component 102 mayfurther represent or include a lens, a shutter, and/or other associatedcomponents along with the vacuum package assembly for capturing infraredimage data. Image capture component 102 may further include temperaturesensors (or temperature sensors may be distributed within system 100) toprovide temperature information to processing component 104 as tooperating temperature of image capture component 102.

In one aspect, the infrared image data (e.g., infrared video data) maycomprise non-uniform data (e.g., real image data) of an image, such asscene 101. Processing component 104 may be adapted to process theinfrared image data (e.g., to provide processed image data), store theinfrared image data in memory component 108, and/or retrieve storedinfrared image data from memory component 108. For example, processingcomponent 104 may be adapted to process infrared image data stored inmemory component 108 to provide processed image data and information(e.g., captured and/or processed infrared image data).

Control component 106 comprises, in one embodiment, a user input and/orinterface device, such as a rotatable knob (e.g., potentiometer), pushbuttons, slide bar, keyboard, etc., that is adapted to generate a userinput control signal. Processing component 104 may be adapted to sensecontrol input signals from a user via control component 106 and respondto any sensed control input signals received therefrom. Processingcomponent 104 may be adapted to interpret such a control input signal asa parameter value, as generally understood by one skilled in the art. Inone embodiment, control component 106 may comprise a control unit (e.g.,a wired or wireless handheld control unit) having push buttons adaptedto interface with a user and receive user input control values. In oneimplementation, the push buttons of the control unit may be used tocontrol various functions of the system 100, such as autofocus, menuenable and selection, field of view, brightness, contrast, noisefiltering, high pass filtering, low pass filtering, and/or various otherfeatures as understood by one skilled in the art.

Display component 110 comprises, in one embodiment, an image displaydevice (e.g., a liquid crystal display (LCD) or various other types ofgenerally known video displays or monitors). Processing component 104may be adapted to display image data and information on the displaycomponent 110. Processing component 104 may be adapted to retrieve imagedata and information from memory component 108 and display any retrievedimage data and information on display component 110. Display component110 may comprise display electronics, which may be utilized byprocessing component 104 to display image data and information (e.g.,infrared images). Display component 110 may be adapted to receive imagedata and information directly from image capture component 102 via theprocessing component 104, or the image data and information may betransferred from memory component 108 via processing component 104.

Optional sensing component 112 comprises, in one embodiment, one or moresensors of various types, depending on the application or implementationrequirements, as would be understood by one skilled in the art. Thesensors of optional sensing component 112 provide data and/orinformation to at least processing component 104. In one aspect,processing component 104 may be adapted to communicate with sensingcomponent 112 (e.g., by receiving sensor information from sensingcomponent 112) and with image capture component 102 (e.g., by receivingdata and information from image capture component 102 and providingand/or receiving command, control, and/or other information to and/orfrom one or more other components of system 100).

In various implementations, sensing component 112 may provideinformation regarding environmental conditions, such as outsidetemperature, lighting conditions (e.g., day, night, dusk, and/or dawn),humidity level, specific weather conditions (e.g., sun, rain, and/orsnow), distance (e.g., laser rangefinder), and/or whether a tunnel orother type of enclosure has been entered or exited. Sensing component112 may represent conventional sensors as generally known by one skilledin the art for monitoring various conditions (e.g., environmentalconditions) that may have an effect (e.g., on the image appearance) onthe data provided by image capture component 102.

In some implementations, optional sensing component 112 (e.g., one ormore of sensors) may comprise devices that relay information toprocessing component 104 via wired and/or wireless communication. Forexample, optional sensing component 112 may be adapted to receiveinformation from a satellite, through a local broadcast (e.g., radiofrequency (RF)) transmission, through a mobile or cellular networkand/or through information beacons in an infrastructure (e.g., atransportation or highway information beacon infrastructure), or variousother wired and/or wireless techniques.

In various embodiments, components of system 100 may be combined and/orimplemented or not, as desired or depending on the application orrequirements, with system 100 representing various functional blocks ofa related system. In one example, processing component 104 may becombined with memory component 108, image capture component 102, displaycomponent 110, and/or optional sensing component 112. In anotherexample, processing component 104 may be combined with image capturecomponent 102 with only certain functions of processing component 104performed by circuity (e.g., a processor, a microprocessor, a logicdevice, a microcontroller, etc.) within image capture component 102.Furthermore, various components of system 100 may be remote from eachother (e.g., image capture component 102 may comprise a remote sensorwith processing component 104, etc. representing a computer that may ormay not be in communication with image capture component 102).

FIG. 2 shows a block diagram illustrating a specific implementationexample for an infrared camera 200 in accordance with one or moreembodiments. Infrared camera 200 may represent a specific implementationof system 100 (FIG. 1), as would be understood by one skilled in theart.

Infrared camera 200 (e.g., a microbolometer readout integrated circuitwith bias-correction circuitry and interface system electronics)includes a readout integrated circuit (ROIC) 202, which may include themicrobolometer unit cell array having one or more contacts coupled tomicrobolometer bridges via vertical legs as disclosed herein, controlcircuitry, timing circuitry, bias circuitry, row and column addressingcircuitry, column amplifiers, and associated electronics to provideoutput signals that are digitized by an analog-to-digital (A/D)converter 204. The A/D converter 204 may be located as part of orseparate from ROIC 202.

The output signals from AID converter 204 are adjusted by anon-uniformity correction circuit (NUC) 206, which applies temperaturedependent compensation as would be understood by one skilled in the art.After processing by NUC 206, the output signals are stored in a framememory 208. The data in frame memory 208 is then available to imagedisplay electronics 210 and a data processor 214, which may also have adata processor memory 212. A timing generator 216 provides systemtiming.

Data processor 214 generates bias-correction data words, which areloaded into a correction coefficient memory 218. A data register loadcircuit 220 provides the interface to load the correction data into ROIC202. In this fashion, variable circuitry such as variable resistors,digital-to-analog converters, biasing circuitry, which control voltagelevels, biasing, frame timing, circuit element values, etc., arecontrolled by data processor 214 so that the output signals from ROIC202 are uniform over a wide temperature range.

It should be understood that various functional blocks of infraredcamera 200 may be combined and various functional blocks may also not benecessary, depending upon a specific application and specificrequirements. For example, data processor 214 may perform variousfunctions of NUC 206, while various memory blocks, such as correctioncoefficient memory 218 and frame memory 208, may be combined as desired.

FIG. 3 shows a physical layout diagram of a microbolometer 300 inaccordance with an embodiment of the invention. Microbolometer 300includes a bridge portion 302 having a light sensor 304 and bridgecontacts 306 that couple sensor 304 to a first end of legs 308. Legs 308each couple sensor 304 to one of contacts 310.

Each contact 310 may couple one or more associated microbolometers 300to associated readout circuitry of a readout integrated circuit (ROIC,not shown). For example, a first contact 310 may be used to provide areference or bias voltage to the microbolometer and a second contact 310may be used to a signal path from the microbolometer to the ROIC bywhich signals corresponding to infrared light absorbed by themicrobolometer can be read out. Further descriptions of ROIC andmicrobolometer circuits may be found in U.S. Pat. No. 6,028,309, whichis incorporated by reference in its entirety herein for all purposes.

Sensor 304 may be arranged to convert incident light such as infraredlight into detectable electrical signals based on changes in electricalproperties of the sensor (e.g., changes in resistivity) due to changesin temperature of the sensor when the light is incident. According to anembodiment, sensor 304 may include a resistive material, which may beformed of a high temperature coefficient of resistivity (TCR) material(e.g., vanadium oxide (VOx), titanium oxide (TiOx), or amorphoussilicon). The resistive material may be suspended above the ROIC onbridge 302 and coupled to its contacts 310 via legs 308.

According to various embodiments, each contact 310 may be attached to aportion of a leg 308 that bends downward toward the ROIC (e.g., contact310 may be formed on a substrate such as the ROIC and leg 308 mayinclude a portion that runs at a non-perpendicular angle to thesubstrate from a first height above the substrate such as the height ofthe bridge downward to the substrate contact) and/or each contact 310may include a portion that extends downward (e.g., in the negativez-direction of FIG. 3) from leg 308 to the surface of the ROIC. Legs 308may be formed from one or more layers of conductive material such as,for example, titanium, nickel chromium, and/or other suitable conductivematerials.

In order to provide legs 308 having a width and a length that issufficient to provide suitable performance for microbolometer 300without reducing the fill-factor of an array of microbolometers in whichmicrobolometer 300 is included, legs 308 may be vertically oriented legsthat run along paths in and/or parallel to the x-y plane of FIG. 3 asshown and have an extended dimension that extends in a directionparallel to the z-direction of FIG. 3. Legs 308 may include bendportions 312. Bend portions 312 may have additional electrical couplingand/or support structures as described in further detail hereinafter.

A plane such as the x-y plane of FIG. 3 may be defined by the bridge ofthe microbolometer (e.g., the bridge may include a planar sensor layersuch as a resistive layer that defines a plane or a plane may be definedthat passes through multiple bridges in a microbolometer array) or bythe surface of a substrate (e.g., an ROIC substrate) to which themicrobolometer array is coupled and disposed above.

FIGS. 4A and 4B respectively show top and cross-sectional views of aconventional microbolometer 400 having horizontally oriented legs 406.As shown in the top view of FIG. 4A, a bridge 402 of microbolometer 400is connected by a bridge contact 404 to horizontally oriented leg 406having an extended dimension of width WP that extends in the x-y planeof FIG. 4A. In the cross sectional view of FIG. 4B, taken along line A-Aof FIG. 4A, it can more easily be seen that contact 404, leg 406, andresistive material 403 of microbolometer 400 all extend along the sameplane or parallel planes that are parallel to the x-y plane of FIG. 4B.

In contrast, FIGS. 5A and 5B respectively show top and cross-sectionalviews of a microbolometer 500 according to an embodiment of the presentdisclosure that includes a vertically oriented leg 308. As shown,vertically oriented leg 308 may have a width Win the x-y plane of FIGS.5A and 5B. Width W may be comparatively smaller than the width WP of aconventional microbolometer leg without sacrificing the overall volumeof the leg by allowing the leg 308 to extend in the vertical direction(e.g., in a direction parallel to the z-direction of FIGS. 5A and 5B) sothat vertical leg 308 is perpendicular to a plane defined by bridge 302(e.g., by resistive material 501 of bridge 302, by bridge contact 306,and/or by an array of bolometer bridges formed at a common height abovean ROIC) and/or a plane defined by a surface of the substrate over whichthe bridge is formed.

As shown, according to an embodiment, a vertical leg 308 may include aconductive (e.g., metal) portion 506 and, if desired, insulatingmaterial 508 on one or more sides of the conductive portion. However,this is merely illustrative. According to various embodiments,conductive portion 506 may be partially or completely surrounded bydielectric material or may be free of dielectric material. Variousexamples of implementations of vertical legs 308 are describedhereinafter in connection with FIGS. 13A-13Q. However, first, processesthat may be used to form vertical bolometer legs such as vertical legs308 of FIGS. 3, 5A, and 5B will be discussed according to variousembodiments.

FIGS. 6A-6F show cross sectional side views of a portion of amicrobolometer array at various stages during production ofmicrobolometer legs for the microbolometer array.

Turning now to FIG. 6A, a portion 601 of a microbolometer array is shownhaving a contact 310 and a bridge 302. As shown, bridge 302 includes asensor layer (e.g., a layer of temperature sensitive resistive materialsuch as VOx) 606 and one or more additional layers 604 such as absorberlayers. As shown, contact 310 may be formed from a vertical conductiveportion such as metal stud 608 and one or more layers such as a metalcontact layer 614 in contact with metal stud 608. Contact 310 mayinclude additional layers such as a dielectric layer 616 disposed overthe metal layer 614 and an additional layer 612 such as a passivationlayer disposed under portions of metal layer 614. As shown, layer 612may be formed on a portion of a top surface 603 of a sacrificial layer600. In some cases, a basket contact or other contact may be utilizedinstead of metal stud 608.

Sacrificial layer 600 may be formed from, for example, polyimide. Layers612 and 616 may be formed from, as examples, silicon dioxide or siliconnitride. Metal layer 614 may be formed from titanium, tungsten, copper,aluminum and/or other known metals.

Metal stud 608 may be conductively coupled to a conductive contact suchas contact 610 of a substrate such as a readout integrated circuit(ROIC) substrate such as a complementary metal-oxide-semiconductor(CMOS) ROIC. In the example of FIG. 6A, contact 610 is disposed in anoverglass layer 602 (e.g., a CMOS overglass layer) of the ROIC. Prior toforming vertical legs between the bridge 302 and the contact 310, bridge302 may be disposed on a sacrificial layer 600 that supports bridge 302and fills a gap between bridges of the microbolometer array and the ROICand runs continuously between the bridges and contacts of themicrobolometer array.

According to one embodiment, a process for forming vertical legs betweenbridge 302 and contact 310 may include depositing and patterning anadditional sacrificial layer 620 on sacrificial layer 600 as shown inFIG. 6B. Patterning the additional sacrificial layer 620 may includeforming openings 622 in the additional sacrificial layer (e.g., at leastpartially between the bridge 302 and the contact 310) so that remainingportions of additional sacrificial layer 620 have vertical sidewalls625. Openings 622 may extend into sacrificial layer 600 or may extendonly to the top surface 603 of sacrificial layer 600 (as examples).

Following the deposition and patterning of additional sacrificial layer620, a dielectric layer 624 may be deposited and patterned so thatportions of the dielectric layer 624 remain on sidewalls 625 ofadditional sacrificial layer 620 in openings 622 as shown in FIG. 6C. Ametal layer such as a leg metal layer 626 may then be deposited overcontact 310, portions of sacrificial layer 600, dielectric layer 624 onsidewalls 625, portions of additional sacrificial layer 620, and bridge302 as shown in FIG. 6D. If desired, openings may be formed in adielectric layer of contact 310 and bridge 302 to expose portions ofmetal layer 614 and sensor layer 606 so that metal layer 626 can bedeposited in contact with metal layer 614 and sensor layer 606. Metallayer 626 may be deposited in a blanket deposition process.

As shown in FIG. 6E, an additional dielectric layer 628 may be depositedover metal layer 626 and then metal layer 626 and additional dielectriclayer 628 may be etched (e.g., in a masked spacer etch process) toremove portions of metal layer 626 and additional dielectric layer 628from sacrificial layer 600 and additional sacrificial layer 620. In thisway, a dielectric-metal-dielectric stack may be formed vertically onsidewalls 625 of openings 622. Portions of thedielectric-metal-dielectric stack that are continuously coupled with theportions on sidewalls 625 may also remain on contact 310 and bridge 302,thereby forming bridge contact 306 and a leg metal contact with metallayer 614 of contact 310.

Dielectric layers 624 and 628 may be formed from, as examples, silicondioxide or a silicon nitride. Metal layer 626 may be a single metallayer formed form a homogeneous film of a single material or may includemultiple materials (e.g., multiple layers of the same or differentmaterials formed in multiple deposition operations). For example, metallayer 626 may be formed from titanium, tungsten, copper, aluminum and/orother known metals.

As shown in FIG. 6F, sacrificial layers 600 and 620 may then be removedto release bridge 302 and vertical legs 308 which remain suspended abovethe ROIC with a space 650 interposed between the vertical legs and theROIC. Although the vertical legs 308 of FIG. 6F appear to be floating,this is merely because of the particular cross section through thedevice that is shown. It will be understood by one skilled in the artthat vertical legs 308 of FIG. 6F run along the x-y plane of FIG. 6F as,for example, illustrated in FIG. 3 so that metal layer 626 forms acontinuous conductive path between bridge contact 306 and contact 310.Vertical legs 308 of FIG. 6F may include at least a portion that runsnon-perpendicularly to a plane defined by the surface 699 of substrate602. For example, vertical legs 308 may run along a path that isparallel to the surface 699. In another example, vertical legs 308 mayrun along a path that includes a portion that is parallel to surface 699and an additional portion that bends downward toward surface 699 at anon-perpendicular angle.

The process illustrated by FIGS. 6A-6F is merely illustrative. Accordingto various embodiments, vertical legs for a microbolometer array may beformed using other processes. For example, in one embodiment, a processsuch as the process shown in FIGS. 7A-7F may be performed to formvertical legs that are disposed below the plane at which bridge 302 isformed (e.g., in contrast with the vertical legs of FIG. 6F that aredisposed substantially in a common plane with bridge 302).

Turning now to FIG. 7A, a portion 701 of a microbolometer array is shownhaving a contact 310 and a bridge 302. As shown, bridge 302 includes asensor layer (e.g., a layer of temperature sensitive resistive materialsuch as VOx) 709 and one or more additional layers 707 such as absorberlayers. As shown, contact 310 may be formed from a vertical conductiveportion such as metal stud 708 and one or more layers such as a metalcontact layer 714 in contact with metal stud 708. Contact 310 mayinclude additional layers such as a dielectric layer 716 disposed overthe metal layer 714 and an additional layer 712 such as a passivationlayer disposed under portions of metal layer 714. As shown, passivationlayer 712 may be formed on a portion of a top surface 703 of asacrificial layer 700.

Sacrificial layer 700 may be formed from, for example, polyimide. Layers712 and 716 may be formed from, as examples, silicon dioxide or siliconnitride. Metal layer 714 may be formed from titanium, tungsten, copper,aluminum and/or other known metals.

Metal stud 708 (or, in some cases, a basket-shaped contact) may beconductively coupled to a conductive contact such as contact 750 of areadout integrated circuit (ROIC) such as a complementarymetal-oxide-semiconductor (CMOS) ROIC. In the example of FIG. 7A,contact 750 is disposed in an overglass layer 702 (e.g., a CMOSoverglass layer) of the ROIC. Prior to forming vertical legs between thebridge 302 and the contact 310, bridge 302 may be disposed on asacrificial layer 700 that supports bridge 302 and fills a gap betweenbridges of the microbolometer array and the ROIC and runs continuouslybetween the bridges and contacts of the microbolometer array.

According to one embodiment, a process for forming vertical legs betweenbridge 302 and contact 310 may include forming openings 704 in thesacrificial layer 700 that supports bridge 302 (e.g., by etching throughsurface 703) as shown in FIG. 7B. Openings 704 may be formed in aportion of sacrificial layer 700 that is disposed at least partiallybetween the bridge 302 and the contact 310 so that openings 704 havevertical sidewalls 705 at various locations between bridge 302 andcontact 310. As shown, sidewalls 705 may be located substantially belowa plane defined by bridge 302 (e.g., the x-y plane of FIG. 7B).

As shown in FIG. 7C, a dielectric layer 706 may be deposited andpatterned so that portions of the dielectric layer 706 remain onsidewalls 705 of sacrificial layer 700 in openings 704. Openings such asopenings 713 in layers 707 of bridge 302 and dielectric layer 716 mayalso be formed to expose portions of sensor layer 709 and metal layer714 respectively as shown in FIG. 7D.

A metal layer such as a leg metal layer 710 may then be deposited overcontact 310, portions of sacrificial layer 700, dielectric layer 706 onsidewalls 705, and bridge 302 as shown in FIG. 7E. Metal layer 710 maybe deposited in a blanket deposition process. As shown, portions ofmetal layer 710 may be formed within openings 713 (see FIG. 7D) and incontact with sensor layer 709 and metal layer 714.

An additional dielectric layer 711 (FIG. 7F) may be deposited over metallayer 710 and metal layer 710 and additional dielectric layer 711 may beetched (e.g., in a masked spacer etch process) to remove portions ofmetal layer 710 and additional dielectric layer 711 from sacrificiallayer 700. In this way, a dielectric-metal-dielectric stack may beformed vertically on sidewalls 705 of openings 704 and portions of thedielectric-metal-dielectric stack that are continuously coupled with theportions on sidewalls 705 may also remain on contact 310 and bridge 302,thereby forming bridge contact 306 and a leg metal contact with metallayer 714 of contact 310.

Dielectric layers 706 and 711 may be formed from, as examples, silicondioxide or a silicon nitride. Metal layer 710 may be a single metallayer formed form a homogeneous film of a single material or may includemultiple materials (e.g., multiple layers of the same or differentmaterials formed in multiple deposition operations). For example, metallayer 710 may be formed from titanium, tungsten, copper, aluminum and/orother known metals.

As shown in FIG. 7F, sacrificial layer 700 may then be removed torelease bridge 302 and vertical legs 308 formed from metal layer 710 anddielectric layers 706 and 711 that partially surround metal layer 710.As shown, vertical legs 308 remain suspended above the ROIC with a space720 interposed between the vertical legs and the ROIC. In this way,vertical legs 308 may be formed perpendicular to the x-y plane of FIG.7F and run along a path (e.g., as illustrated in FIG. 3) that isdisposed below the x-y plane of FIG. 7F between bridge 302 and contact310 so that metal layer 710 forms a continuous conductive path betweenbridge contact 306 and contact 310 via legs 308.

Vertical legs 308 of FIG. 7F may include at least a portion that runsnon-perpendicularly to a plane defined by the surface 799 of substrate702. For example, vertical legs 308 may run along a path that isparallel to the surface 799. In another example, vertical legs 308 mayrun along a path that includes a portion that is parallel to surface 799and an additional portion that bends downward toward surface 799 atanon-perpendicular angle.

In the example of FIG. 7F, the legs that couple bridge 302 to contact310 may include vertical portions 308 and horizontal portions 718 thatextend between bridge 302 and a first end of vertical leg 308 andbetween a second opposing end of vertical leg 308 and contact 310. Invarious embodiments, legs 308 may include any suitable combination ofvertical and horizontal portions for providing sufficient performancefor the microbolometer while avoiding reduction of the fill factor ofthe microbolometer array due to the area occupied by the legs.

FIGS. 8A-8C are cross sectional side views of a portion of amicrobolometer array at various stages during formation of vertical legsthat illustrate yet another alternative process of vertical legformation.

Turning now to FIG. 8A, a portion 801 of a microbolometer array is shownhaving a contact 310 and a bridge 302. As shown, bridge 302 includes asensor layer (e.g., a layer of temperature sensitive resistive materialsuch as VOx) 806 and one or more additional layers 807 such as absorberlayers. As shown, contact 310 may be formed from a vertical conductiveportion such as metal stud 803 and one or more layers such as a metalcontact layer 814 in contact with metal stud 803. Contact 310 mayinclude additional layers such as a dielectric layer 816 disposed overthe metal layer 814 and an additional layer 812 such as a passivationlayer disposed under portions of metal layer 814 and covering a topsurface of a sacrificial layer 800. Passivation layer 812 may extendbetween bridge 302 and contact 310 on the top surface sacrificial layer800.

Sacrificial layer 800 may be formed from, for example, polyimide. Layers812 and 816 may be formed from, as examples, silicon dioxide or siliconnitride. Metal layer 814 may be formed from titanium, tungsten, copper,aluminum and/or other known metals.

Metal stud 803 (or in some cases, a basket-shaped contact) may beconductively coupled to a conductive contact such as contact 809 of areadout integrated circuit (ROIC) such as a complementarymetal-oxide-semiconductor (CMOS) ROIC. In the example of FIG. 8A,contact 809 is disposed in an overglass layer 802 (e.g., a CMOSoverglass layer) of the ROIC. Prior to forming vertical legs between thebridge 302 and the contact 310, bridge 302 may be disposed on asacrificial layer 800 that supports bridge 302 and fills a gap betweenbridges of the microbolometer array and the ROIC and runs continuouslybetween the bridges and contacts of the microbolometer array.

According to one embodiment, a process for forming vertical legs betweenbridge 302 and contact 310 may include forming openings 804 in thesacrificial layer 800 that supports bridge 302 and in the passivationlayer 812 that is disposed on the sacrificial layer as shown in FIG. 8A.Openings 804 may be formed in a portion of sacrificial layer 800 andpassivation layer 812 that is at least partially disposed between thebridge 302 and the contact 310 so that openings 804 have verticalsidewalls 805 at various locations between bridge 302 and contact 310.As shown, sidewalls 805 may be formed from a portion of sacrificiallayer 800 and passivation layer 812.

A metal layer such as a leg metal layer 808 may then be deposited (e.g.,over contact 310, on portions of the top surface of passivation layer812, on sidewalls 805 in contact with both sacrificial layer 800 andpassivation layer 812, on portions of sacrificial layer 800 in openings804, and on bridge 302) before a dielectric layer 810 is deposited(e.g., over metal layer 808) and then metal layer 808, dielectric layer810, and passivation layer 812 may be patterned (e.g., in a maskedspacer etch process) so that metal layer 808 remains on some of thesidewalls of openings 804, as shown in FIG. 8B. In this way, a metal legmay be formed vertically on some of the sidewalls of openings 804 andhorizontal portions 818 having metal layer 808 interposed betweenpassivation layer 812 and dielectric layer 810 may also remain onsacrificial layer 800.

Dielectric layer 810 may be formed from, as examples, silicon dioxide ora silicon nitride. Metal layer 808 may be a single metal layer formedform a homogeneous film of a single material or may include multiplematerials (e.g., multiple layers of the same or different materialsformed in multiple deposition operations). For example, metal layer 808may be formed from titanium, tungsten, copper, aluminum and/or otherknown metals.

As shown in FIG. 8C, sacrificial layer 800 may then be removed torelease bridge 302 and vertical legs 308 with horizontal portions 818.As shown, vertical legs 308 including horizontal portions 818 remainsuspended above the ROIC with a space 820 interposed between thevertical legs and the ROIC. Vertical legs having some horizontalportions such as those shown in FIG. 8C may be less prone to movementand/or damage than legs having only vertical portions. Vertical legs 308including horizontal portions 818 may form a continuous conductive pathbetween bridge contact 306 and contact 310 via legs 308.

Vertical legs 308 of FIG. 8C may include at least a portion that runsnon-perpendicularly to a plane defined by the surface 899 of substrate802. For example, vertical legs 308 may run along a path that isparallel to the surface 899. In another example, vertical legs 308 mayrun along a path that includes a portion that is parallel to surface 899and an additional portion that bends downward toward surface 899 atanon-perpendicular angle.

It will be appreciated that the processes described above in connectionwith FIGS. 6A-8C can be modified, rearranged, and/or omitted to formvertical bolometer legs having various shapes, sizes, orientations, andarrangements as desired for various purposes. FIGS. 9, 10, 11, 12,13A-13Q, 14, and 15 show various arrangements of vertical legs andassociated contacts or bridges that can be formed for microbolometerarrays. In particular, FIGS. 9 and 10 show portions of a microbolometerarray (prior to release by removal of a sacrificial layer) havingvertical legs formed below the plane of the bridge in the vicinity of acontact and a bridge, respectively, of a microbolometer, according toone embodiment. FIGS. 11 and 12 show portions of a microbolometer arrayhaving vertical legs formed below the plane of the bridge in thevicinity of a contact and a bridge, respectively, of a microbolometer,according to another embodiment. FIGS. 13A-13Q show various arrangementsof metal and insulation for vertical legs for a microbolometer. FIGS. 14and 15 show portions of a microbolometer array having vertical legsformed at or above the plane of the bridge in the vicinity of a contactand a bridge, respectively, of a microbolometer, according to anotherembodiment.

As shown in FIG. 9, at a particular stage of production, a portion ofmetal layer 714 may be formed on sacrificial layer 700 and a portion ofdielectric layer 706 may extend over the portion of metal layer 714 thatis formed on the sacrificial layer, over a vertical portion of metallayer 714 that is formed on stud 708, and over a horizontal portion ofmetal layer 714 that is formed on top of stud 708 such that the portionof dielectric layer 706 that is disposed above the top surface ofsacrificial layer 700 is symmetric on multiple sides of stud 708.Sacrificial layer 700 may then be removed.

A process that results in the structure of FIG. 9 for contact 310 mayalso form a bridge as shown in FIG. 10 according to an embodiment. Asshown in FIG. 10, bridge 302 may include bridge dielectric layers 1000and 1002 disposed on opposing sides of sensor layer 606. Dielectriclayer 706 may extend vertically from a vertical leg structure 308 andover a portion of bridge dielectric 1002. Metal layer 710 may cover theportion of dielectric layer 706 that extends vertically from thevertical leg structure 308 and over the portion of bridge dielectric1002 and the metal layer may extend through bridge dielectric 1002 andleg dielectric 706 to contact sensor layer 606.

In an alternative embodiment, as shown in FIG. 11, metal layer 710 maybe asymmetric about the top of stud 708 so that metal layer 710 remainsin contact with metal layer 714 of contact 310 on the side of stud 708on which the vertical legs 308 are formed, thereby increasing thecontact area between layers 710 and 714. Following formation of thestructures of FIG. 11 as shown, sacrificial layer 700 may be removed.

A process that results in the structure of FIG. 11 for contact 310 mayalso form a bridge as shown in FIG. 12 according to an embodiment. Asshown in FIG. 12, a portion of metal layer 710 may be formed directly ona portion of bridge dielectric 1002 so that metal layer 710 passes overthe portion of bridge dielectric 1002 and through bridge dielectric 1002to contact sensor layer 606.

FIGS. 13A-13Q each show a cross sectional view of an exemplaryimplementation of a vertical bolometer leg such as vertical legs 308 asdescribed herein. As shown in FIG. 13A, a vertical bolometer leg mayinclude a substantially vertical conductive (e.g., metal) layer 1300that is disposed between first and second substantially verticaldielectric layers 1302 and 1304 that have a common height H with thevertical conductive layer 1300. In the configuration of FIG. 13A, thevertical leg may have a width that is substantially the same along theheight of the vertical leg and substantially equal to the sum of thewidths of the layers 1300, 1302, and 1304.

In general, a vertical bolometer leg may have a first dimension (e.g., aheight H) that extends in a direction that is perpendicular to a planedefined by the associated bolometer bridge and/or a substrate, a seconddimension (e.g., a width W) that extends in a direction that is parallelto the plane of the bridge and/or the substrate, and a third dimensionthat extends along and defines a signal path, where the path may includea portion that extends in a direction parallel to the plane of thebridge and/or the substrate, and where the second dimension issubstantially smaller than the first dimension.

As shown in FIG. 13B, in one embodiment, dielectric layer 1302 mayextend above the top of conductive layer 1300 and run horizontally overthe top of conductive layer 1300 and dielectric layer 1304. As shown inFIG. 13C, in one embodiment, conductive layer 1300 may have a heightthat is shorter than the height of dielectric layer 1302 and dielectriclayer 1302 may run underneath the bottom of conductive layer 1300 anddielectric layer 1304.

As shown in FIG. 13D, in one embodiment, dielectric layer 1302 mayextend above the top of conductive layer 1300 and run horizontally overthe top of conductive layer 1300 and dielectric layer 1304 andconductive layer 1300 may have a height that is shorter than the heightof dielectric layer 1302 and dielectric layer 1304 may run underneaththe bottom of conductive layer 1300 to dielectric layer 1302. As shownin FIG. 13E, in one embodiment, conductive layer 1300 may have a heightthat is shorter than the height of dielectric layer 1302, dielectriclayer 1304 may run underneath the bottom of conductive layer 1300 todielectric layer 1302, and a horizontal dielectric layer 1306 may coverthe top of layers 1300, 1302, and 1304.

As shown in FIG. 13F, in one embodiment, conductive layer 1300 anddielectric layers 1302 and 1304 may have a common height and ahorizontal dielectric layer 1306 may cover the top of layers 1300, 1302,and 1304. As shown in FIG. 13G, in one embodiment, conductive layer 1300may have a vertical portion and a horizontal portion such thatconductive layer has, in cross section, an “L” shape. In theconfiguration of FIG. 13G, dielectric layer 1304 runs vertically alongthe vertical portion of conductive layer 1300 and horizontally under thevertical and horizontal portions of conductive layer 1300 and dielectriclayer 1302 runs vertically along the vertical portion of conductivelayer 1300, horizontally over the top of the horizontal portion ofconductive layer 1300, and vertically past the horizontal portion ofconductive layer 1300 to the bottom of the vertical leg.

As shown in FIG. 13H, in one embodiment, conductive layer 1300 may befree of any surrounding dielectric material. As shown in FIG. 13I, inone embodiment, conductive layer 1300 may have one side covered bydielectric layer 1304 and an opposing side that is free of dielectricmaterial. As shown in FIG. 13J, in one embodiment, a conductive layer1300 that has one side covered by dielectric layer 1302 and an opposingside that is free of dielectric material may have a height that isshorter than the height of the vertical leg and dielectric layer 1302may run underneath the bottom of conductive layer 1300. As shown in FIG.13K, in one embodiment, a conductive layer 1300 that has one sidecovered by dielectric layer 1302 and an opposing side that is free ofdielectric material may have a vertical portion and a horizontal portionthat runs over the top of dielectric layer 1302.

As shown in FIG. 13L, in one embodiment, a conductive layer 1300 thathas one side covered by dielectric layer 1304 and an opposing side thatis free of dielectric material may have a first vertical portion, ahorizontal portion that runs over the top of dielectric layer 1304, anda second vertical portion that is offset from the first verticalportion. In the configuration of FIG. 13L, dielectric layer 1304 mayhave a vertical portion that runs along the first vertical portion ofconductive layer 1300 and a horizontal portion that runs under the firstvertical portion of conductive layer 1300 to the second vertical portionof conductive layer 1300.

As shown in FIG. 13M, conductive layer 1300 may include a verticalportion and a horizontal portion 1308 that extends horizontally from thebottom of the vertical portion of conductive layer 1300 so thatconductive layer 1300 and horizontal portion 1308 form an “L” shape. Inthe example of FIG. 13M, conductive layer 1300 is covered on a firstside by dielectric (insulating) layer 1302, on another side bydielectric (insulating) layer 1304, and along a bottom surface ofhorizontal portion 1308 by insulating (dielectric layer 1312).

As shown in FIG. 13N, in one embodiment, horizontal portion 1308 and thepart of the vertical portion that is below the top surface of thevertical portion may be substantially surrounded by one or moredielectric layers such as dielectric layers 1302, 1304, and 1312 so thatthe top end of the vertical portion of conductive layer 1300 is free ofdielectric material.

As shown in FIG. 13O, in one embodiment, conductive portion 1300 mayhave a vertical portion, a first horizontal portion that extends in afirst direction from the top of the vertical portion, a secondhorizontal portion that extends in an opposing second direction from thebottom of the vertical portion, and an additional portion that fills thespace beneath a horizontal dielectric layer 1304 formed under the firsthorizontal portion. In the configuration of FIG. 13O, the firsthorizontal portion, the vertical portion and top of the secondhorizontal portion of conductive layer 1300 are covered on one side bydielectric layer 1302.

As shown in FIG. 13P, in one embodiment, conductive layer 1300 may havea vertical portion, a first horizontal portion that extends in a firstdirection from the top of the vertical portion, and a second horizontalportion that extends in an opposing second direction from the bottom ofthe vertical portion. In the configuration of FIG. 13P, the firsthorizontal portion, the vertical portion and top of the secondhorizontal portion of conductive layer 1300 are covered on one side bydielectric layer 1302 and dielectric layer 1304 runs under and fills thespace under the first horizontal portion of conductive layer 1300. Asshown in FIG. 13Q, a conductive layer having a vertical portion, a firsthorizontal portion that extends in a first direction from the top of thevertical portion, and a second horizontal portion that extends in anopposing second direction from the bottom of the vertical portion may besubstantially surrounded by an insulating material 1312.

As shown in FIG. 14, at a particular stage of production for verticalbolometer legs formed above and perpendicular to surface 603 of asacrificial layer such as sacrificial layer 600 (e.g., the sacrificiallayer upon which the bridge structures for one or more microbolometersare formed), a portion of metal layer 614 may be formed on sacrificiallayer 600 and a portion of dielectric layer 624 may extend over theportion of metal layer 614 that is formed on the sacrificial layer, overa vertical portion of metal layer 614 that is formed on stud 608, andover a horizontal portion of metal layer 614 that is formed on top ofstud 608. Dielectric layer 624, leg metal layer 626, and dielectriclayer 628 may forma horizontal portion 1400 that extends horizontallyfrom contact 310 and turns perpendicularly to form vertical leg portion308. Sacrificial layer 600 may then be removed.

A process that results in the structure of FIG. 14 for contact 310 mayalso form a bridge as shown in FIG. 15 according to an embodiment. Asshown in FIG. 15, bridge 302 may include bridge dielectric layers 1500and 1502 disposed on opposing sides of sensor layer 606. Dielectriclayer 624, metal layer 626, and dielectric layer 628 may form a stackthat includes vertical leg portions 308 and a portion 1504 that extendshorizontally from a vertical leg portion 308 to bridge 302. As shown,metal layer 626 may cover a portion of dielectric layer 624 that extendshorizontally from the vertical leg structure 308 and over a portion ofbridge dielectric 1502 and may pass through bridge dielectric 1502 andleg dielectric 624 to contact sensor layer 606.

FIG. 16 shows a top view of a portion of a vertical leg 308 in a bendregion 312. FIGS. 17 and 18 show cross sectional side views of exemplaryimplementations of the bend region 312 taken along the line x-x of FIG.16. As shown in FIG. 17, according to one embodiment, bend region 312may include a pad 1700 formed at the bottom of a vertical conductivelayer 1702 that is interposed between vertical dielectric layers 1704and 1706 of the vertical leg. Pad 1700 may be formed from metal,dielectric materials, or a combination of metal and dielectric materials(as examples). As shown in FIG. 18, according to one embodiment, bendregion 312 may include a metal pad 1800 formed over the top of verticalconductive layer 1702 and vertical dielectric layers 1704 and 1706 ofthe vertical leg. Pad 1800 may be formed from metal, dielectricmaterials, or a combination of metal and dielectric materials (asexamples).

FIG. 19 is a cross sectional side view of a portion of a microbolometerarray at a particular stage of production showing how, in oneembodiment, at least a portion of a vertical leg structure may be formedbeneath the bridge 302 of a microbolometer. As shown in FIG. 19, bridge302 may include a sensor layer 606 disposed between bridge dielectriclayers 1908 and 1910. Bridge dielectric layer 1910 may be formed on afirst sacrificial layer 1904 that is interposed between bridgedielectric layer 1910 and a vertical leg structure 1906 that runsbeneath the bridge dielectric layer 1910 and overglass 1902 of an ROICfor the microbolometer array. At the stage of production shown in FIG.19, a second sacrificial layer 1900 may be disposed between the verticalleg structure 1906 and overglass 1902.

In the configuration shown in FIG. 19, sensor layer 606 of bridge 302includes a vertical portion that runs downward from the bridge 302 andturns horizontally to form a portion of bridge contact 306. As shown, aconductive layer such as conductive layer 1911 may couple sensormaterial 606 in bridge contact region 306 to the vertical leg structure1906. Vertical leg structure 1906 may extend to a contact such as a studcontact or basket contact that couples the vertical leg structure 1906to a contact on the ROIC (e.g., a contact formed partially or completelywithin overglass layer 1902). Vertical leg structure 1906 may couple toa dedicated contact structure for the bridge 302 underneath which it isformed and/or may be coupled to a shared contact with an adjacentmicrobolometer.

FIG. 20 is a flowchart of illustrative operations that may be performedfor forming vertical microbolometer legs for coupling a microbolometerbridge to a ROIC contact structure according to an embodiment.

At block 2000, an imaging device having contact structures and bolometerbridge structures such as microbolometer bridge structures may beprovided. The imaging device may include a partially fabricated focalplane array on which a sacrificial layer such as a polyimide layer isformed on a substrate such as a readout integrated circuit and thebridge structures are formed on the sacrificial layer. In someembodiments, an etch stop layer may be formed on the sacrificial layer.However, in other embodiments, the sacrificial layer may be free of anyetch stop material. The contact structures may include an electricalcontact on the readout integrated circuit and, if desired conductiveelements that extend from the electrical contact on the ROIC throughsome or all of the sacrificial layer. The conductive elements mayinclude a stud or a basket contact and, if desired, one or moreadditional structures such as passivation layers, metal layers, and/ordielectric layers formed over the conductive elements.

At block 2002, an additional sacrificial layer may be deposited andpatterned over or on the sacrificial layer. In embodiments, in which anetch stop layer is provided on the sacrificial layer, the additionalsacrificial layer may be deposited on the etch stop layer so thatportions of the etch stop layer are formed between the sacrificial layerand the additional sacrificial layer. Patterning the additionalsacrificial layer may include etching the additional sacrificial layerto form openings in the additional sacrificial layer at least partiallybetween the bridge structures and the contact structures.

At block 2004, a first leg dielectric material may be formed at least onsidewalls of the openings in the patterned additional sacrificial layer.Forming the first leg dielectric material on the sidewalls of theopenings may include depositing the first leg dielectric layer andperforming a spacer etch of the first leg dielectric layer. The etch mayalso leave portions of the first leg dielectric layer on portions of thecontact structures and/or the bridge structures as desired.

At block 2006, one or more conductive layers such as a leg metal layermay be deposited (e.g., using a blanket metal deposition) and patternedon the first leg dielectric material on the sidewalls of the openingsand over at least some of the contact structures and the bridgestructures. The leg metal layer may be formed in contact with a metallayer of the contact structures and with a sensor layer of the bridgestructures.

At block 2008, a second leg dielectric layer may be deposited andpatterned on the metal layer. Patterning the second leg dielectric layermay include depositing the second leg dielectric layer over the legmetal layer prior to patterning the leg metal layer and performing anin-situ dielectric and metal etch of the leg metal layer and the secondleg dielectric layer.

At block 2010, the sacrificial layer and the additional sacrificiallayer may be removed to release the bridge structures and the verticalleg structures formed from the first and second leg dielectric layersand the leg metal layers so that the bridge and legs are suspended abovethe readout integrated circuit and the contact structures are coupled tothe bridge structures by the vertical leg structures. In embodiments, inwhich an etch stop layer is provided on the sacrificial layer, portionsof the etch stop layer may also be removed.

FIG. 21 is a flowchart of illustrative operations that may be performedfor forming vertical microbolometer legs for coupling a microbolometerbridge to a ROIC contact structure according to another embodiment.

At block 2100, an imaging device having contact structures and bolometerbridge structures such as microbolometer bridge structures may beprovided. The imaging device may include a partially fabricated focalplane array on which a sacrificial layer such as a polyimide layer isformed on a readout integrated circuit and the bridge structures areformed on the sacrificial layer. The contact structures may include anelectrical contact on the readout integrated circuit and, if desiredconductive elements that extend from the electrical contact on the ROICthrough some or all of the sacrificial layer. The conductive elementsmay include a stud or a basket contact and, if desired, one or moreadditional structures such as passivation layers, metal layers, and/ordielectric layers formed over the conductive elements.

At block 2102, the sacrificial layer may be etched to form openings inthe sacrificial layer at least partially between the bridge structuresand the contact structures.

At block 2104, a first leg dielectric material may be formed at least onsidewalls of the openings in the sacrificial layer. Forming the firstleg dielectric material on the sidewalls of the openings may includedepositing the first leg dielectric layer and performing a spacer etchof the first leg dielectric layer. The etch may also be performed toleave portions of the first leg dielectric layer on portions of thecontact structures and/or the bridge structures as desired.

At block 2106, openings may be formed in a dielectric layer of thecontact structures and the bridge structures. Forming the openings inthe dielectric layer of the contact structures and the bridge structuresmay expose portions of a metal layer of the contact structures and/or asensor layer of the bridge structures.

At block 2108, one or more conductive layers such as a leg metal layermay be deposited (e.g., using a blanket metal deposition) and patternedon the first leg dielectric material on the sidewalls of the openingsand over at least some of the contact structures and the bridgestructures. The leg metal layer may be formed in contact with theexposed portions of the metal layer of the contact structures and thesensor layer of the bridge structures.

At block 2110, a second leg dielectric layer may be deposited andpatterned on the metal layer. Patterning the second leg dielectric layermay include depositing the second leg dielectric layer over the legmetal layer prior to patterning the leg metal layer and performing anin-situ dielectric and metal etch of the leg metal layer and the secondleg dielectric layer.

At block 2112, the sacrificial layer may be removed to release thebridge structures and the vertical leg structures formed from the firstand second leg dielectric layers and the leg metal layers so that thebridge and legs are suspended above the readout integrated circuit andthe contact structures are coupled to the bridge structures by thevertical leg structures.

FIG. 22 is a flowchart of illustrative operations that may be performedfor forming vertical microbolometer legs for coupling a microbolometerbridge to a ROIC contact structure according to another embodiment.

At block 2200, an imaging device having contact structures and bolometerbridge structures such as microbolometer bridge structures may beprovided. The imaging device may include a partially fabricated focalplane array on which a sacrificial layer such as a polyimide layer isformed on a readout integrated circuit, a passivation layer is formed onat least a portion of the sacrificial layer and the bridge structuresare formed on the sacrificial layer. The contact structures may includean electrical contact on the readout integrated circuit and, if desiredconductive elements that extend from the electrical contact on the ROICthrough some or all of the sacrificial layer. The conductive elementsmay include a stud or a basket contact and, if desired, one or moreadditional structures such a portion of the passivation layer, metallayers, and/or dielectric layers formed over the conductive elements.

At block 2202, the sacrificial layer and the passivation layer may beetched to form openings in the sacrificial layer and the passivationlayer at least partially between the bridge structures and the contactstructures.

At block 2204, one or more conductive layers such as a leg metal layermay be deposited (e.g., using a blanket metal deposition) and patternedon the sidewalls of the openings and over at least some of the contactstructures, the bridge structures, and portions of the passivation layeron the sacrificial layer.

At block 2206, a leg dielectric layer may be deposited and patterned onthe metal layer. Patterning the leg dielectric layer may includedepositing the leg dielectric layer over the leg metal layer prior topatterning the leg metal layer and performing an in-situ dielectric andmetal etch of the leg metal layer and the second leg dielectric layer.

At block 2208, the sacrificial layer may be removed to release thebridge structures and the vertical leg structures formed from portionsof the passivation layer, the leg dielectric layer and the leg metallayer so that the bridge and legs are suspended above the readoutintegrated circuit and the contact structures are coupled to the bridgestructures by the vertical leg structures.

The process described above for forming vertical microbolometer legs aremerely illustrative. According to various embodiments, vertical legs fora microbolometer array may be formed using other processes. For example,in one embodiment, a process such as the process shown in FIGS. 23A-23Fmay be performed to form vertical legs using an etch stop layer.

FIGS. 23A-23F show cross sectional side views of a portion of amicrobolometer array at various stages during production ofmicrobolometer legs for the microbolometer array.

Turning now to FIG. 23A, a portion 2398 of a microbolometer array isshown having a contact 310 and a bridge 302. As shown, bridge 302includes a sensor layer (e.g., a layer of temperature sensitiveresistive material such as VOx) 2306 and one or more additional layers2304 such as absorber layers. As shown, contact 310 may be formed from avertical conductive portion such as metal stud 2308 and one or morelayers such as a metal contact layer 2314 in contact with metal stud2308. Contact 310 may include additional layers such as a passivationlayer 2316 disposed under portions of metal layer 2314. As shown, anadditional layer such as an etch stop layer 2303 (e.g., a layer ofdielectric material) may be formed on sacrificial layer 2300 and mayextend to form a portion of bridge 302 and/or contact 310.

Sacrificial layer 2300 may be formed from, for example, polyimide.Layers 2303 and 2316 may be formed from, as examples, silicon dioxide orsilicon nitride. Metal layer 2314 may be formed from titanium, tungsten,copper, aluminum and/or other known metals.

Metal stud 2308 may be conductively coupled to a conductive contact suchas contact 2310 of a substrate such as a readout integrated circuit(ROIC) substrate such as a complementary metal-oxide-semiconductor(CMOS) ROIC. In the example of FIG. 23A, contact 2310 is disposed in anoverglass layer 2302 (e.g., a CMOS overglass layer) of the ROIC. Priorto forming vertical legs between the bridge 302 and the contact 310,bridge 302 may be disposed on sacrificial layer 2300 so that sacrificiallayer 2300 fills a gap between bridges of the microbolometer array andthe ROIC and runs continuously between the bridges and contacts of themicrobolometer array.

According to one embodiment, a process for forming vertical legs betweenbridge 302 and contact 310 may include depositing and patterning anadditional sacrificial layer 2320 on etch stop layer 2303 as shown inFIG. 23B. Patterning the additional sacrificial layer 2320 may includeforming openings 2322 in the additional sacrificial layer (e.g., atleast partially between the bridge 302 and the contact 310) so thatremaining portions of additional sacrificial layer 2320 have verticalsidewalls 2325. Openings 2322 may extend to the top surface 2301 of etchstop layer 2303.

Following the deposition and patterning of additional sacrificial layer2320, a dielectric layer 2324 may be deposited and patterned so thatportions of the dielectric layer 2324 remain on sidewalls 2325 ofadditional sacrificial layer 2320 in openings 2322 as shown in FIG. 23C.A metal layer such as a leg metal layer 2326 may then be deposited overcontact 310, portions of etch stop layer 2303, dielectric layer 2324 onsidewalls 2325, portions of additional sacrificial layer 2320, andbridge 302 as shown in FIG. 23D. If desired, openings may be formed inportions of etch stop layer 2303 that are disposed over contact 310 andbridge 302 to expose portions of metal layer 2314 and sensor layer 2306so that metal layer 2326 can be deposited in contact with metal layer2314 and sensor layer 2306. Metal layer 2326 may be deposited in ablanket deposition process.

As shown in FIG. 23E, an additional dielectric layer 2328 may bedeposited over metal layer 2326 and then metal layer 2326 and additionaldielectric layer 2328 may be etched (e.g., in a masked spacer etchprocess) to remove portions of metal layer 2326 and additionaldielectric layer 2328 from etch stop layer 2303 and additionalsacrificial layer 2320. In this way, a dielectric-metal-dielectric stackmay be formed vertically on sidewalls 2325 of openings 2322. Portions ofthe dielectric-metal-dielectric stack that are continuously coupled withthe portions on sidewalls 2325 may also remain on contact 310 and bridge302, thereby forming bridge contact 306 and a leg metal contact withmetal layer 2314 of contact 310.

Dielectric layers 2324 and 2328 may be formed from, as examples, silicondioxide or a silicon nitride. Metal layer 2326 may be a single metallayer formed form a homogeneous film of a single material or may includemultiple materials (e.g., multiple layers of the same or differentmaterials formed in multiple deposition operations). For example, metallayer 2326 may be formed from titanium, tungsten, copper, aluminumand/or other known metals.

As shown in FIG. 23F, sacrificial layers 2300 and 2320 and portions ofetch stop layer 2303 may then be removed to release bridge 302 andvertical legs 308 which remain suspended above the ROIC with a space2350 interposed between the vertical legs and the ROIC. Vertical legs308 of FIG. 23F may include at least a portion that runsnon-perpendicularly to a plane defined by the surface 2399 of substrate2302. For example, vertical legs 308 may run along a path that isparallel to the surface 2399. In another example, vertical legs 308 mayrun along a path that includes a portion that is parallel to surface2399 and an additional portion that bends downward toward surface 2399at anon-perpendicular angle.

FIG. 24 shows a cross-sectional side view of a microbolometer bridgethat is coupled to legs formed beneath the bridge, according to anembodiment. In the example of FIG. 24, bridge 302 includes a sensorlayer 2400 formed substantially between bridge dielectric layers 2402and 2404. Sensor layer 240 (e.g., a temperature sensitive resistivematerial, such as VOx) may include one or more horizontal portions thatextend in a plane that is parallel to the surface of a substrate overwhich bridge 302 is formed and may include portions 2406 that extenddownward from the horizontal portions in the direction of the substrate(e.g., perpendicularly to the surface of the substrate. Portions 2406may extend to contact one or more legs such as legs 2420 formed beneaththe bridge 302 (e.g., disposed at least partially between bridge 302 andthe substrate over which the bridge is disposed).

As shown in FIG. 24, legs 2420 are formed form a conductive materialhaving a horizontal portion 2408 in contact with sensor layer 2306 and avertical portion 2410 that extends perpendicularly to horizontal portion2408. However, this is merely illustrative. In various embodiments, legs2420 may include vertical and/or horizontal portions and/or may becovered partially or completely in an insulating material as in, forexample, any of the examples described herein.

Illustrative operations that may be performed to form a bridge of thetype shown in FIG. 24 are shown in FIG. 25.

At block 2500, an imaging device having contact structures that areformed on and/or in a sacrificial layer may be provided. The imagingdevice may include a partially fabricated focal plane array on which asacrificial layer such as a polyimide layer is formed on a substratesuch as a readout integrated circuit substrate. The contact structuresmay include an electrical contact on the substrate and, if desiredconductive elements that extend from the electrical contact on the ROICthrough some or all of the sacrificial layer. The conductive elementsmay include a stud or a basket contact and, if desired, one or moreadditional structures such as passivation layers, metal layers, and/ordielectric layers formed over the conductive elements.

At block 2502, openings may be formed in the sacrificial layer.

At block 2504, a first leg dielectric material may be formed at least onsidewalls of the openings in the sacrificial layer. Forming the firstleg dielectric material on the sidewalls of the openings may includedepositing the first leg dielectric layer and performing a spacer etchof the first leg dielectric layer.

At block 2506, one or more conductive layers such as a leg metal layermay be deposited (e.g., using a blanket metal deposition) and patternedon the first leg dielectric material that is on the sidewalls of theopenings and over at least some of the contact structures. The leg metallayer may be formed in contact with a metal layer of the contactstructures.

At block 2508, a second leg dielectric layer may be deposited andpatterned on the leg metal layer. Patterning the second leg dielectriclayer may include depositing the second leg dielectric layer over theleg metal layer prior to patterning the leg metal layer and performingan in-situ dielectric and metal etch of the leg metal layer and thesecond leg dielectric layer.

At block 2510, an additional sacrificial layer may be deposited on thesacrificial layer.

At block 2512, one or more bolometer bridge contacts may be formed inthe second sacrificial layer.

At block 2514, a first bridge dielectric layer may be deposited.

At block 2516, one or more contacts may be formed in the first bridgedielectric layer and the underlying second leg dielectric layer on theleg metal layer for connection to the leg metal layer.

At block 2518, a bolometer resistive sensing material (e.g., atemperature sensitive resistive material such as VOx) may be depositedand patterned to form sensor layers of the bolometer bridges.

At block 2520, as second bridge dielectric material may be deposited andpatterned, thereby defining a bridge area of each microbolometer formedover at least portions of the underlying leg materials.

At block 2522, the sacrificial layer and the additional sacrificiallayer may be removed to release the bridge structures and the verticalleg structures so that the bridge and legs that are formed beneath thebridge are suspended above the substrate and the contact structures arecoupled to the bridge structures by the vertical leg structures.

In conventional approaches to manufacturing bolometers, patterningoccurred along the x- and y-dimensions and a material thickness wasdeposited as a sheet film in the z-dimension. The sheet film controlleda thickness of a device in the z-dimension. FIG. 26 shows a top-downview of a bolometer. FIG. 27 shows a cross-section of a leg along a line2605 of FIG. 26. In particular, the cross-section is a cut along theline 2605 in the x-direction (e.g., horizontal width direction) andlooking in the y-direction (e.g., in the direction of the leg length).The leg includes an insulator material 2705, an electrically conductivelayer 2710 disposed on the insulator material 2705, and an insulatormaterial 2715 disposed on the electrically conductive layer 2710. Theinsulator material 2705, the electrically conductive layer 2710, and theinsulator material 2715 are disposed one on top of the other along thez-dimension. It is noted that FIG. 27 shows an example in which amaterial deposition thickness (MDT) is around the same for the insulatormaterial 2705, the electrically conductive layer 2710, and the insulatormaterial 2715. However, the MDTs need not be the same between thesematerials/layers.

As pixel sizes decrease, an amount of area in the x- and y-direction isreduced. To increase sensitivity, a thickness of bolometer materials isalso reduced. Such reduction in the thickness of the bolometer materialsis associated with a corresponding reduction in an amount of structuralsupport the bolometer has built into it. To add rigidity to a bolometerof such a reduced size, a vertical component may be added to thebolometer structure.

FIG. 28 shows rigidity provided by a vertical component as an example. Aflat piece of metal may have a total mass of M. If this flat piece ofmetal is supported at both ends, the flat piece of metal can support anamount of weight W₁. If that same metal having a total mass of M isformed into an I-beam structure or some other similar structure having avertical component, the metal can hold a weight W₂ larger than theweight W₁.

With smaller pixels, material thicknesses are reduced to support adesired performance. As materials are thinned, rigidity diminishes untillegs of the bolometer are unable to support a mass of the bolometerabsent introduction of a vertical component added into the legs to addrigidity/support to the pixel. In a vertical leg design, materialthickness may control more than the z-dimension. Variation in the heightof the vertical component in the leg impacts thermal and electricalproperties of the leg. Such impacts to the thermal and electricalproperties may have an impact to the performance of the bolometer.

FIG. 29 shows a top-down view of a microbolometer array having verticallegs in accordance with an embodiment. FIG. 30A shows a cross-section ofa leg along a line 2905 of FIG. 29. In particular, the cross-section isa cut along the line 2905 in the x-direction (e.g., horizontal widthdirection) and looking in the y-direction (e.g., in the direction of theleg length). The leg has a z-shaped cross-section (e.g., also consideredan s-shaped cross-section). The leg includes an insulator material 3005,an electrically conductive layer 3010 disposed on the insulator material3005, and an insulator material 3015 disposed on the electricallyconductive layer 3010. The insulator material 3005, the electricallyconductive layer 3010, and the insulator material 3015 are disposed oneon top of the other along the z-dimension. The z-shaped cross-sectionprovides a path from a bridge to a contact. The contact may be a contactof a substrate. Portions 2910 and 2915 of the bolometer show regions oftransition from corresponding legs to corresponding contacts. It isnoted that FIG. 30A shows an example in which an MDT is around the samefor the insulator material 3005, the electrically conductive layer 3010,and the insulator material 3015. However, the MDTs need not be the samebetween these materials/layers.

As shown with respect to FIG. 30A, a serpentine-shaped cross-section ofthe leg has a first section (e.g., left-side section or lower section),a second section (e.g., right-side section or upper section)substantially parallel to the first section, and a third section (e.g.,middle section) joining the first section and the second section. Tocouple the bridge to the contact of the substrate, the leg may extendbetween the bridge and the contact in a first direction (e.g.,x-direction) and/or a second direction (e.g., y-direction) substantiallyparallel to a plane of the substrate. The serpentine-shaped crosssection (e.g., s-shaped or z-shaped) is maintained along the x- and/ory-directions. In this regard, the first section and the second sectionextend along the first direction and/or second direction substantiallyparallel to the plane. The third section joins the first and secondsections in a third direction (e.g., z-direction) that is substantiallyperpendicular to the plane.

With regard to the particular cross-section shown in FIG. 30A of theleg, the leg has a segment 3020 associated with the first section, asegment 3025 associated with the second section, and a segment 3030associated with the third section. The segment 3030 is adjacent to thesegment 3020 and the segment 3025. Each of the segments 3020, 3025, and3030 has a first dimension (e.g., width) that extends in the x-directionsubstantially parallel to the plane of the surface of the substrate anda second dimension (e.g., height) that extends in the z-directionsubstantially perpendicular to the plane. For the segments 3020 and3025, the first dimension is greater than the second dimension. For thesegment 3030, the first dimension is less than the second dimension.Each of the segments 3020, 3025, and 3030 has a respective portion ofthe insulator material 3005, a respective portion of the electricallyconductive layer 3010, and a respective portion of the insulatormaterial 3015. The insulator material 3005 is formed on a first sidewallof the electrically conductive layer 3010 and a first side of theelectrically conductive layer 3010. The insulator material 3015 isformed on a second sidewall of the electrically conductive layer 3010and a second side of the electrically conductive layer 3010. The firstsidewall is opposite the second sidewall. The first sidewall issubstantially perpendicular to the first side. The first side isopposite the second side. In some aspects, twosegments/sections/portions may be referred to as being substantiallyperpendicular if an angle between the segments/sections/portions iswithin ±10° of 90°. In some aspects, two segments/sections/portions maybe referred to as being substantially parallel if an angle between thesegments/sections/portions is within ±10° of 0°.

Various approaches may be utilized to define a vertical component of aleg. Each approach is associated with a complexity, variability, andmaterial (e.g., which affects performance). Deposited films may havedesirable uniformities across a wafer and have small variations from runto run (e.g., wafer to wafer). In this manner, a deposited film may beutilized to control a vertical component. In an aspect, a bolometer mayinclude a deposited film of conductive material (e.g., metal) and adeposited film of non-conductive material (e.g., insulator). Dry etchesassociated with conventional CMOS processing may be utilized toselectively remove one type of film to another (e.g., a metal can beremoved where it is not protected by an insulator). For instance, aninsulator is an etch stop for a metal etch, and a metal is an etch stopfor an insulator etch. A leg may have an insulator and/or a metal lefton the leg after etching, which affects bolometer performance.

In some aspects, a z-height of the leg may be reduced (e.g., relative tothat shown in FIG. 30A) while creating additional rigidity for thebolometer. FIG. 30B illustrates a cross-section of a leg having a heightsmaller than that of the leg of FIG. 30A, in accordance with anembodiment. The leg of FIG. 30B has a segment 3035 (e.g., associatedwith a first section), a segment 3040 (e.g., associated with a secondsection), and a segment 3045 (e.g., associated with a third section). Inan aspect, the segments 3035, 3040, and 3045 may be considered ascorresponding to the segments 3020, 3025, and 3030, respectively, of theleg of FIG. 30A. In some cases, control of the height across the wafermay be more relevant than an actual average of the z-dimension giventhat the z-dimension exceeds a desired threshold to meet a minimumrigidity for the bolometer, depending on the specific implementation.

While the third section is substantially perpendicular to the firstsection and the second section in FIGS. 30A and 30B, in variousembodiments the third section is at an angle (e.g., nominally at anangle) relative to the first and second sections. In this regard, such athird section is slanted compared to the third section shown in FIGS.30A and 30B. FIG. 31 illustrates an example cross-section of a leg 3100having a slanted section in accordance with one or more embodiments. Thecross-section of the leg 3100 has a first section, a second sectionsubstantially parallel to the first section, and a third section that isslanted and joins the first and second sections. With regard to theparticular cross-section shown in FIG. 31 of the leg 3100, the leg 3100has a segment 3105 associated with the first section, a segment 3110associated with the second section, and a segment 3115 associated withthe third section. The segment 3115 is at around 45° relative to ahorizontal axis (e.g., left and right direction) associated with thesegments 3105 and 3110. In other examples of leg structures, the middlesection may be at a different angle from that shown in FIGS. 30A-30B(e.g., substantially perpendicular to its adjacent sections) and FIG. 31(e.g., at around 45° relative to its adjacent sections). By way ofnon-limiting examples, the middle section may be at an angle betweenaround 30° to 60° relative to the horizontal axis associated with thesegments 3105 and/or 3110.

The leg 3100 has a dielectric layer 3120, a dielectric layer 3125disposed on the dielectric layer 3120, a leg metal layer 3130 disposedon the dielectric layer 3125, and a dielectric layer 3135 disposed onthe leg metal layer 3130. In this regard, the leg metal layer 3130 issurrounded on at least two opposite sides by the dielectric layers 3135and 3125. The leg 3100 has a tail 3140 of the dielectric layer 3120. Agap 3145 is between the tail 3140 and a side of the dielectric layer3125, such that the tail 3140 faces the dielectric layer 3125. In anaspect, the tail 3140 may be formed due to etching operations performedto form the leg 3100.

In one or more embodiments, leg manufacturing processes may include, ormay be based on, directed self-assembly (DSA) (e.g., polymer-based),oxide patterning, and/or others. Each process has several variations.Different processes may be associated with different process complexity,exposure resolution, overlay, etc. In some aspects, each process hasdevice feature order variation. For instance, legs, contact, and bridgecan potentially be processed in any order. Each device feature order isassociated with its set of tradeoffs (e.g., complexity, cost, etc.). Insome aspects, various paths/options for facilitating vertical legmanufacture may allow for processing of the legs separate from a bridge.In some cases, leg materials can be independent (e.g., completelyindependent) from the bridge. In some cases, some leg materials are onthe bridge (e.g., in contact with the bridge). Higher independencebetween the legs and the bridge is generally associated with a morecomplex process.

As an example, FIG. 32 shows a top-down view of a bolometer having abridge 3320, vertical legs, and contacts 3315 and 3350, in which anoxide approach is utilized to manufacture the bolometer, in accordancewith an embodiment. In some cases, the oxide approach may be associatedwith lower process complexity than a DSA approach. The oxide approachmay facilitate model correlation/feedback. FIG. 33 shows a cross-sectionof a leg along a line 3205 of FIG. 32. The bolometer includes asubstrate 3305, a pad 3310, the contact 3315 (e.g., a basket contact, astud contact), the bridge 3320, and portions 3325, 3330, 3335, 3340, and3345 of a leg, and the contact 3350. The portions 3325 and 3330 providea path between the contact 3315 and the bridge 3320, with the portion3330 of the leg transitioning to the bridge 3320. The portions 3335,3340, and 3345 provide a path between the contact 3350 and the bridge3320. The portion 3335 transitions to the bridge 3320.

As another example, FIG. 34 shows a top-down view of a bolometer havinga bridge 3520, vertical legs, and contacts 3515 and 3560, in which a DSAapproach is utilized to manufacture the bolometer, in accordance with anembodiment. FIG. 35 shows a cross-section of a leg along a line 3405 ofFIG. 34 in accordance with an embodiment. The bolometer includes asubstrate 3505, a pad 3510, the contact 3515 (e.g., a basket contact),the bridge 3520, portions 3525, 3530, 3535, 3540, 3545, 3550, and 3555of a leg, and the contact 3560. The portions 3525 and 3530 provide apath between the contact 3515 and the bridge 3520, with the portion 3530of the leg transitioning to the bridge 3320. The portions 3535, 3540,3545, 3550, and 3555 provide a path between the contact 3560 and thebridge 3520. The portion 3535 transitions to the bridge 3520. Azoomed-in view of a portion of the leg is shown in FIG. 35. The legincludes a vertically stacked arrangement of a SiO₂, a leg metal, andSi. A portion of the SiO₂ is disposed on the leg metal. A portion of theSiO₂ is below the leg metal and the Si. Such materials are provided byway of non-limiting examples.

FIGS. 36A through 36N illustrate cross-sectional side views associatedwith an example process for forming a bolometer in accordance with anembodiment. FIG. 37 illustrates a top-down view corresponding to thecross-sectional side view of FIG. 36N in accordance with an embodiment.

In FIG. 36A, a readout circuit wafer 3600 (e.g., ROIC wafer) isprovided. The readout circuit wafer 3600 includes a substrate 3601, anoverglass layer 3602, and a metal layer 3603. The overglass layer 3602is disposed on the substrate 3601. The metal layer 3603 extends throughthe overglass layer 3602. Bolometer processing is performed on thereadout circuit wafer 3600 to form a bolometer that is coupled to thereadout circuit wafer 3600. An example of bolometer processing isdescribed with reference to FIGS. 36B through 360. In FIG. 36B, pads3604 are disposed on the readout circuit wafer 3600. The pads 3604 mayform part of one or more metal layers. In FIG. 36C, a release layer 3606(e.g., also referred to as a sacrificial layer) is disposed on theoverglass layer 3602 and the pads 3604, and a protection layer 3608 isdisposed on the release layer 3606. The release layer 3606 may be apolyimide coating. The protection layer 3608 may be deposited as a thinsheet film over the release layer 3606.

In FIG. 36D, a metal layer 3612 is disposed on the protection layer3608, and a dielectric layer 3614 is disposed on the metal layer 3612.The metal layer 3612 may be a titanium layer. In some cases, the metallayer 3612 may form or may be referred to as an absorber layer. In thesecases, this absorber layer may be formed of, for example, titanium. Themetal layer 3612 may be utilized as an etch stop layer for subsequentetching operations (e.g., to allow etching of an oxide layer(s) down tothe metal layer 3612). The dielectric layer 3614 may be formed of Si₃N₄.The metal layer 3612 and the dielectric layer 3614 may be deposited asthin sheet films.

In FIG. 36E, the metal layer 3612 and the dielectric layer 3614 areetched. To facilitate etching of the metal layer 3612 and the dielectriclayer 3614, one or more patterning operations may be performed. Ingeneral, etching operations are preceded by depositing and patterning ofphotoresist to define portions of material to be etched/removed, andeach etching operation may be isotropic or anisotropic. Patterning mayinclude depositing a photoresist layer and exposing the photoresistlayer appropriate to define portions of the metal layer 3612 and thedielectric layer 3614 to be etched. Etching may be performed on themetal layer 3612 and the dielectric layer 3614, and the photoresistlayer then removed. In an aspect, a first etching operation (e.g.,reactive ion etch) may be performed to etch down through the dielectriclayer 3612 to the metal layer 3614. A second etching operation (e.g., ofa different chemistry from the first etching operation) may be performedto etch down through the metal layer 3614 to the protection layer 3608.Blocks 3616 may identify portions of the metal layer 3612 and thedielectric layer 3614 that remain after etching. In some cases, theblocks 3616 may represent mask material utilized to facilitatepatterning and etching to obtain the metal layer 3612 and the dielectriclayer 3614 as shown in FIG. 36E.

In FIG. 36F, a resistive layer 3622 (e.g., VOx layer, TiOx layer,amorphous silicon) and a dielectric layer 3624 are disposed. Theresistive layer 3622 is disposed such that the resistive layer 3622 isin contact with the protection layer 3608, the metal layer 3612, and thedielectric layer 3614. The dielectric layer 3624 is disposed on theresistive layer 3622. The dielectric layer 3624 may be a cap layer forthe resistive layer 3622. In FIG. 36G, the resistive layer 3622 and thedielectric layer 3624 are etched. Such etching may etch the resistivelayer 3622 and the dielectric layer 3624 such that they define athermistor of the bolometer to be formed. A block 3630 identifies aportion of the resistive layer 3622 and the dielectric layer 3624 thatremains after etching. In some cases, the block 3630 may represent maskmaterial utilized to facilitate patterning and etching to obtain theresistive layer 3622 and the dielectric layer 3624 as shown in FIG. 36G.The block 3630 may be considered as defining a sensing portion of abridge and a non-sensing portion of the bridge. The sensing portion ofthe bridge has the resistive layer 3622, whereas the non-sensing portionof the bridge does not have the resistive layer 3622. In FIG. 36G, thesensing portion of the bridge is directly below the block 3630 andassociated with a region 3660, and the non-sensing portion of the bridgeis associated with regions 3662 and 3664 adjacent to the region 3660.The regions 3662 and 3664 may form a region that surrounds the region3660. In some embodiments, the non-sensing portion of the bridge mayhave perforations defined therein to reduce thermal mass associated withthe bridge. An example of a bridge having perforations defined in thebridge's non-sensing portion is described with respect to FIG. 49.

In FIG. 36H, a dielectric layer 3632 is disposed such that thedielectric layer 3632 is in contact with the protection layer 3608, themetal layer 3612, the dielectric layer 3614, the resistive layer 3622,and the dielectric layer 3624. In some cases, the dielectric layer 3632is formed of the same material as the dielectric layer 3624 and/or 3614.In FIG. 36I, the resistive layer 3622 and the dielectric layer 3624 areetched to expose the resistive layer 3622. A block 3634 identifies aportion of the resistive layer 3622 and the dielectric layer 3624 thatare not removed after etching. In some cases, the block 3634 mayrepresent mask material utilized to facilitate patterning and etching toobtain the resistive layer 3622 and the dielectric layer 3624 as shownin FIG. 36I. In FIG. 36J, a leg metal layer 3636 is disposed such thatthe leg metal layer 3636 is in contact with the dielectric layer 3632,the resistive layer 3622, and the dielectric layer 3624. A portion ofthe leg metal layer 3636 on the resistive layer 3622 may be referred toas resistive layer contacts (e.g., thermistor contacts). The leg metallayer 3636 may be made of, for example, titanium, tungsten, copper, orother metals. In FIG. 36K, a dielectric layer 3638 is disposed on theleg metal layer 3636. In an aspect, the dielectric layer 3638 may bedisposed using very thin sheet films (e.g., atomic layer deposition(ALD)).

In FIG. 36L, a portion of the protection layer 3608, the dielectriclayer 3632, the leg metal layer 3636, and the dielectric layer 3638 areetched. In some cases, performing of a metal etch and an oxide etch maybe alternated as appropriate to etch the layers 3632, 3636, and 3638 oneat a time. Blocks 3640 identify portions of the layer 3608, 3632, 3636,and 3638 that remain after etching. In some cases, the block 3640 mayrepresent mask material utilized to facilitate patterning and etching toobtain the layers 3608, 3632, 3636, and 3638 as shown in FIG. 36L. In anaspect, various patterning and etching operations are performed to forma bridge 3644. In FIG. 36M, a portion of the layers 3608, 3632, 3636,and 3638 are etched. Blocks 3642 identify portions of the layer 3608,3632, 3636, and 3638 that remain after etching. In some cases, the block3642 may represent mask material utilized to facilitate patterning andetching to obtain the layers 3608, 3632, 3636, and 3638 as shown in FIG.36M. FIGS. 36L and 36M help define vertical legs 3646 and 3647 in FIG.36N. In an aspect, FIG. 36L is associated with opening/cutting a bottomof a leg structure, and FIG. 36M is associated with opening/cutting atop of a leg structure.

In FIGS. 36N and 37, various operations are performed to form a contact3648 (e.g., basket contact) between the pads 3604 and the vertical leg3647. A drilling operation may be performed to open a trench (e.g., alsoreferred to as an opening) through the release layer 3606 to the readoutcircuit wafer 3600. In some cases, the drilling operation may includeetching operations. The contact 3648 and the vertical legs 3646collectively connect the bridge 3644 to the substrate 3601 (e.g., anROIC). The contact 3648 may be made of, for example, aluminum. Variousmaterial deposition operations (e.g., basket metal depositionoperations), patterning operations, etching operations, and/or otheroperations are performed to obtain the structure as shown in FIG. 36N.The etching operations cause a formation of tails 3650 and 3652 (e.g.,also referred to as residual tabs). The tails 3650 and 3652 are portionsof the protection layer 3608 that remain after etching, whereas portionsof the metal layer 3612 (previously disposed on the tails 3650 and 3652)have been removed due to the etching operation(s). In this regard, inFIG. 36N, a gap 3654 and 3656 is above the tail 3650 and 3652,respectively. The tails 3650 and 3652 of the protection layer 3608 facethe dielectric layer 3632. In FIGS. 36N and 37, a sensing portion of thebridge 3644 is associated with a region 3666, and anon-sensing portionof the bridge 3644 is associated with a region 3668 surrounding theregion 3666. In some embodiments, the bridge 3644 may include a metallayer (e.g., an absorber layer) disposed on the dielectric layer 3638. Acap layer (e.g., SiO₂) may be disposed on the metal layer.

FIGS. 38A through 38D illustrate cross-sectional side views associatedwith an example process for forming a contact in accordance with anembodiment. The contact may be utilized to couple a bridge to a readoutcircuit wafer. Various features of FIGS. 38A through 38D may beimplemented in the same or similar manner as corresponding features ofFIGS. 36A-36N and/or other figures.

In FIG. 38A, a structure having a bridge 3844 is formed. In an aspect,the structure of FIG. 38A may be utilized as a starting structure priorto forming of a contact to couple the bridge 3844 to the readout circuitwafer. The readout circuit wafer includes a substrate 3801, an overglasslayer 3802, and a metal layer 3803. Pads 3804 are disposed on thereadout circuit wafer. The structure further includes a release layer3806 (e.g., polyimide), a protection layer 3808, a metal layer 3812(e.g., MUP layer formed of titanium), a dielectric layer 3614 (e.g.,oxide), a resistive layer 3822 (e.g., VO_(x) layer), and a dielectriclayer 3838 (e.g., thin sheet film). It is noted this structure directlyconnects the bridge 3844 to the readout circuit wafer without utilizinga leg structure. In an aspect, in processing steps subsequent to FIG.38D, legs may optionally be defined for connecting the bridge 3844 tothe readout circuit wafer. If leg structures are to be formed, the metallayer 3818 may be utilized as a leg metal layer.

In FIG. 38B, the dielectric layer 3838 is etched. A block 3846identifies a portion of the dielectric layer 3838 that is etched out. Insome cases, the block 3846 may represent mask material utilized tofacilitate patterning and etching to obtain the dielectric layer 3838 asshown in FIG. 38B. In FIG. 38C, to define a trench 3850, a portion ofthe release layer 3806, the protection layer 3808, the metal layer 3812,the dielectric layer 3814, and the metal layer 3818 is removed. Thelayers 3806, 3808, 3812, 3814, 3818, and 3838 may be etched using one ormore etching operations. A block 3848 identifies a portion of the layers3806, 3808, 3812, 3814, 3818, and 3838 that are etched out. In somecases, the block 3848 may represent one or more mask material utilizedto facilitate patterning and etching to obtain the layers 3806, 3808,3812, 3814, 3818, and 3838 as shown in FIG. 38C. In an aspect, the metallayer 3812 and/or the metal layer 3818 may be utilized as a hard maskfor etching of the release layer 3806 (e.g., polyimide etch). In FIG.38D, a contact metal layer 3852 is disposed. The contact metal layer3852 is disposed on at least one of the pads 3804 (e.g., left pad inFIG. 38D) to couple the bridge 3844 to the readout circuit wafer. Thecontact metal layer 3852 is in contact with the release layer 3806, theprotection layer 3808, the dielectric layer 3814, the metal layer 3812,the metal layer 3818, the dielectric layer 3838, and one of the pads3804. Although a basket contact is formed in FIGS. 38A-38D, in otherembodiments a stud contact or other type of contact may be formed.Additional operations may be performed on the structure shown in FIG.38D, such as removing the release layer 3806, to form a bolometer. It isnoted that legs may optionally be defined in the structure of FIG. 38Dsuch that the legs are utilized to couple the bridge 3844 to the readoutcircuit wafer. Examples of additional operations, including legformation, are described with respect to FIGS. 39A through 39D.

FIGS. 39A through 39D illustrate cross-sectional side views associatedwith an example process for forming legs after a contact to a readoutcircuit wafer has been formed in accordance with an embodiment. FIG. 40illustrates a top-down view corresponding to the cross-sectional sideview of FIG. 39D in accordance with an embodiment. Various features ofFIGS. 39A through 39D may be implemented in the same or similar manneras corresponding features of FIGS. 36A-36N and/or other figures. In someembodiments, the process shown in relation to FIGS. 39A through 39D maybe utilized to form the bolometer of FIGS. 34 and 35.

In FIG. 39A, a structure having a bridge 3944 and a contact metal layer3922 for coupling the bridge 3944 to the readout circuit wafer areformed. In an aspect, the structure of FIG. 39A may be utilized as astarting structure prior to forming legs for coupling the bridge 3944 tothe readout circuit wafer. The readout circuit wafer includes asubstrate 3901, an overglass layer 3902, and a metal layer 3903. Pads3904 are disposed on the readout circuit wafer. The structure furtherincludes a release layer 3906 (e.g., polyimide), a protection layer 3908(e.g., poly cap layer), a metal layer 3910 (e.g., formed of titanium), adielectric layer 3912 (e.g., nitride (e.g., Si₃N₄) or oxide (e.g.,SiO₂)), a resistive layer 3914 (e.g., VOx), a leg metal layer 3916, adielectric layer 3918 (e.g., thin film layer formed of SiO₂ or Si₃N₄),and a semiconductor layer 3920. In FIG. 39B, the contact metal layer3922 is etched. A block 3924 identifies a portion of the contact metallayer 3922 that remains after etching. In some cases, the block 3924 mayrepresent a mask material utilized to facilitate patterning and etchingto obtain the contact metal layer 3922 as shown in FIG. 39B.

In FIG. 39C, a portion of each of the dielectric layer 3918, the legmetal layer 3916, the protection layer 3908, and the release layer 3906is etched to define trenches 3926. Blocks 3928 identify portions of thestructure of FIG. 39C that remain after etching. In some cases, theblock 3928 may represent mask material utilized to facilitate patterningand etching to obtain the structure as shown in FIG. 39C. In FIGS. 39Dand 40, the dielectric layer 3918 and the leg metal layer 3916 areetched to expose the semiconductor layer 3920, and the release layer3906 is removed. As a result, legs 3931, 3932, and 3930 are formed. Thelegs 3931 and 3932 are associated with a current pixel (e.g., the bridge3944). The leg 3930 may be associated with a next pixel.

A zoomed-in view of a portion 3934 of the structure of FIG. 39D is shownin FIG. 39E. In particular, the portion 3934 is a portion of a leg ofthe structure. It is noted that materials identified in FIG. 39E areprovided by way of non-limiting example. The leg includes a verticallystacked arrangement of the semiconductor layer 3920 (e.g., Si,poly-styrine), the leg metal layer 3916, and the dielectric layer 3918(e.g., SiO₂). The layers 3920, 3916, and 3918 are disposed on the metallayer 3910. The metal layer 3910 is disposed on the protection layer3908.

FIGS. 41A through 41T illustrate cross-sectional side view associatedwith an example process for forming a bolometer in accordance with anembodiment. FIG. 42 illustrate a top-down view corresponding to thecross-sectional side view of FIG. 41T in accordance with an embodiment.Various features of FIGS. 41A through 41T may be implemented in the sameor similar manner as corresponding features of FIGS. 36A-36N and/orother figures.

In FIG. 41A, a readout circuit wafer 4100 (e.g., ROIC wafer) isprovided. The readout circuit wafer 4100 includes a substrate 4101, anoverglass layer 4102, and a metal layer 4103. Bolometer processing isperformed on the readout circuit wafer 4100 to form a bolometer that iscoupled to the readout circuit wafer 4100. An example of bolometerprocessing is described with reference to FIGS. 41B through 41T. In FIG.41B, pads 4104 are disposed on the readout circuit wafer 4100. The pads4104 may form part of one or more metal layers. In FIG. 41C, a releaselayer 4106 is disposed on the dielectric layer 4102 and on the pads4104, and a protection layer 4108 is disposed on the release layer 4106.In some aspects, one or more alignment marks may be etched in theprotection layer 4108 (e.g., to facilitate alignment for bolometerprocessing using one or more masks). In FIG. 41D, a metal layer 4112(e.g., metal absorber layer) is disposed on the protection layer 4108,and a dielectric layer 4114 (e.g., Si₃N₄/SiO₂) is disposed on the metallayer 4112. In FIG. 41E, the protection layer 4108, the metal layer4112, and the dielectric layer 4114 are etched. Patterning may includedepositing a photoresist layer and exposing the photoresist layerappropriate to define portions of the protection layer 4108, the metallayer 4112, and the dielectric layer 4114 to be etched. A block 4116 mayidentify a portion of the layers 4108, 4112, and 4114 that remain afteretching. In some cases, the block 4116 may represent a mask materialutilized to facilitate patterning and etching to obtain the layers 4108,4112, and 4114 as shown in FIG. 41E.

In FIG. 41F, a dielectric layer 4118 (e.g., thin film oxide layer) and ametal layer 4120 are disposed, and the metal layer 4120 is etched.Blocks 4121 may identify portions of the metal layer 4120 that remainafter etching. In some cases, the blocks 4121 may represent maskmaterial utilized to facilitate patterning and etching to obtain themetal layer 4120 as shown in FIG. 41F. In FIG. 41G, a dielectric layer4122 (e.g., thin film oxide layer), a resistive layer 4124 (e.g., VOxlayer), and a dielectric layer 4126 are disposed. The dielectric layer4122 is in contact with the dielectric layer 4118, the metal layer 4120,and the resistive layer 4124. The dielectric layer 4126 is in contactwith the resistive layer 4124. In FIG. 41H, the resistive layer 4124 andthe dielectric layer 4126 are etched. Such an etch may help define abridge portion of the bolometer to be formed. A block 4128 may identifyportions of the resistive layer 4124 and the dielectric layer 4126 thatremain after etching. In some cases, the blocks 4128 may represent maskmaterial utilized to facilitate patterning and etching to obtain theresistive layer 4124 and the dielectric layer 4126 as shown in FIG. 41H.The block 4128 may be considered as defining a sensing portion of abridge and anon-sensing portion of the bridge. In FIG. 41I, one or morepatterning operations and etching operations are performed to remove(e.g., etch) the release layer 4106, the dielectric layer 4118, and thedielectric layer 4122 to form a trench 4132 down to the readout circuitwafer 4100. In an aspect, a process of defining the trench 4132 (and, insome cases, trenches associated with other pixels of the bolometer) maybe referred to as a reticulation pattern. A block 4130 may identifyportions of the layers 4122, 4118, and 4106 to be removed to form thetrench 4132.

In FIG. 41J, a contact metal layer 4134 is disposed. The contact metallayer 4434 is disposed on at least one of the pads 4104 (e.g., left padin FIG. 41J) to couple the bridge portion of the bolometer to thereadout circuit wafer 4100. The contact metal layer 4134 is in contactwith the release layer 4106, the dielectric layer 4118, the dielectriclayer 4122, and at least one of the pads 4104. The contact metal layer4134 is utilized to form a contact basket. In FIG. 41K, the contactmetal layer 4134 is etched to expose the dielectric layer 4126 and 4122.A block 4136 may identify a portion of the contact metal layer 4134 thatis removed by etching. In some cases, the block 4136 may represent maskmaterial utilized to facilitate patterning and etching to obtain thecontact metal layer 4134 as shown in FIG. 41K. In FIG. 41L, a dielectriclayer 4138 is disposed. In FIG. 41M, the dielectric layer 4138 isetched. A block 4140 may identify a portion of the dielectric layer 4138that remains after etching. In some cases, the block 4140 may representmask material utilized to facilitate patterning and etching to obtainthe dielectric layer 4138 as shown in FIG. 41M. In FIG. 41N, the contactmetal layer 4134 is etched. A block 4142 may identify a portion of thecontact metal layer 4134 that remains after etching. In some cases, theblock 4142 may represent mask material utilized to facilitate patterningand etching to obtain the contact metal layer 4134 as shown in FIG. 41N.

In FIG. 41O, the dielectric layer 4138, the dielectric layer 4126, andthe resistive layer 4124 are etched to expose the resistive layer 4124.A block 4144 may identify a portion of the layers 4138, 4126, and 4124that is removed after etching. In some cases, the block 4144 mayrepresent mask material utilized to facilitate patterning and etching toobtain the layers 4138, 4126, and 4124 as shown in FIG. 410. In FIG.41P, a leg metal layer 4146 is disposed. In FIG. 41Q, the leg metallayer 4146 is etched. Blocks 4148 may identify portions of the leg metallayer 4146 that remain after etching. In some cases, the blocks 4148 mayrepresent mask material utilized to facilitate patterning and etching toobtain the leg metal layer 4146 as shown in FIG. 41Q. In FIG. 41R, adielectric layer 4150 (e.g., thin film layer) is disposed.

In FIG. 41S, portions of the dielectric layer 4112, the dielectric layer4114, the dielectric layer 4118, the dielectric layer 4122, the metallayer 4120, the leg metal layer 4146, and the dielectric layer 4150 areremoved, thus forming a bridge 4153. Blocks 4152 may identify portionsof the layers 4112, 4114, 4118, 4122, 4120, 4146, and 4150 that remainafter etching. In some cases, the blocks 4152 may represent maskmaterial utilized to facilitate patterning and etching to obtain thelayers 4112, 4114, 4118, 4122, 4120, 4146, and 4150 as shown in FIG.41S. In FIGS. 41T and 42, one or more patterning operations and etchingoperations are performed and the release layer 4106 removed to form thebolometer of FIG. 41T. The bolometer includes the bridge 4153 and legs4160 and 4161. The etching operations cause a formation of tails 4154,4156, and 4158. The etching operations cause a formation of tails 4154,4156, and 4158 and gaps 4162, 4164, and 4166, respectively, above thetails 4154, 4156, and 4158. In FIGS. 41T and 42, a sensing portion ofthe bridge 4153 is associated with a region 4170, and a non-sensingportion of the bridge 4153 is associated with a region 4172 surroundingthe region 4170. In some embodiments, the bridge 4153 may include ametal layer (e.g., an absorber layer) disposed on the dielectric layer4126. A cap layer may be disposed on this metal layer.

FIGS. 43A and 43B illustrate views associated with a bolometer 4300having a bridge 4305, vertical legs 4308 and 4310, and contacts 4315 and4320, in accordance with an embodiment. FIG. 43A shows a perspectiveview of the bolometer 4300. FIG. 43B shows a cross-section of thebolometer 4300 along a line 4325. In this regard, the cross-sectionshows a portion 4330 of the bolometer 4300 along the line 4325. In someembodiments, the bolometer 4300 may be formed using techniques that arethe same as or similar to those provided herein. As shown in FIG. 43B,the bolometer 4300 includes a dielectric layer 4335 (e.g., insulator), ametal layer 4340 (e.g., titanium), a dielectric layer 4345 (e.g.,insulator), a resistive layer 4350 (e.g., VOx), a leg metal layer 4355(e.g., titanium, copper), a dielectric layer 4360 (e.g., thininsulator/oxide layer formed of Si₃N₄), a dielectric layer 4365 (e.g.,Si₃N₄), and a dielectric layer 4370 (e.g., SiO₂). The dielectric layer4335 may be referred to as a protection layer.

The metal layer 4340 is disposed on the dielectric layer 4335. Thedielectric layer 4345 is disposed on the metal layer 4340. The resistivelayer 4350 is disposed on the dielectric layer 4345. The dielectriclayer 4370 is disposed on the resistive layer 4350. The leg metal layer4355 is disposed on the resistive layer 4350. The dielectric layer 4360is disposed on the leg metal layer 4355. The dielectric layer 4370 is incontact with the leg metal layer 4355 and the resistive layer 4350. Thecontact 4315 includes a basket fill layer 4375, the leg metal layer4355, the dielectric layer 4365, the dielectric layer 4345, the caplayer 4335, and a leg metal layer 4380. The contact 4320 includes abasket fill layer 4385, the metal layer 4355, the dielectric layer 4365,the dielectric layer 4345, the cap layer 4335, and a leg metal layer4390. The basket fills layers 4375 and 4385 may be made, for example, ofaluminum. The leg metal layers 4380 and 4390 may be made, for example,of titanium, tungsten, copper, or other metals. The dielectric layers4365 and 4345 may be utilized as passivation in the contacts 4315 and4320. Although FIG. 43A shows the contacts 4315 and 4320 asbasket-shaped contacts, in other embodiments, differently shaped contactand/or different types of contacts, such as stud contacts, may beutilized to implement the contacts 4315 and/or 4320.

In some aspects, as shown in FIG. 43B, etching operations performed toobtain the bolometer 4300 form tails 4391 and 4393 of the dielectriclayer 4335. In this regard, the tails 4391 and 4393 remain afteretching, whereas portions of the metal layer 4340 (previously disposedon the tails 4391 and 4393 prior to being etched out) have been removedto form gaps 4392 and 4394 above the tails 4391 and 4393.

The resistive layer 4350 is coupled to the contacts 4315 and 4320 viathe vertical legs 4308 and 4310. In this regard, the leg metal layer4355 of the vertical legs 4308 and 4310 are in contact with theresistive layer 4350. By way of non-limiting examples, the resistivelayer 4350 may include VOx, TiOx, or amorphous silicon. The verticallegs 4308 and 4310 connect to the bridge 4305 and the contacts 4315 and4320. The leg metal layers 4380 and 4390 of the contacts 4315 and 4320,respectively, are connected to a substrate (e.g., of an ROIC). As such,the bridge 4305 is coupled to the substrate via the vertical legs 4308and 4310 and the contacts 4315 and 4320. The contacts 4315 and 4320 maycontact (e.g., physically contact) a metal layer of the substrate. Insome cases, the substrate may have an overglass layer formed thereon.

As non-limiting examples, a thickness of the cap layer 4335, the metallayer 4340, the dielectric layer 4345, the resistive layer 4350, themetal layer 4355, the dielectric layer 4360, the dielectric layer 4370,and the dielectric layer 4365 is 250 Å, 300 Å, 750 Å, 600 Å, 300 Å, 300Å, 300 Å, and 500 Å, respectively. A distance D is a distance between abottom side of the cap layer 4335 and a bottom side of the leg metallayer 4390. A non-limiting example of the distance D may be around 1.5μm. As non-limiting examples, a width W and a height H of a vertical legmay be around 0.24 μm and 0.25 μm, respectively.

FIGS. 44A through 44E illustrate various views associated with abolometer 4400 having a bridge 4405, vertical legs 4408 and 4410, andcontacts 4415 and 4420, in accordance with an embodiment. FIG. 44A showsa perspective view of the bolometer 4400. FIG. 44B shows a zoomed-inview of a portion 4424 of the bolometer 4400. The portion 4424 shows aconnection of the vertical leg 4410 to the bridge 4405. FIG. 44C shows aside-view cross-section of the bolometer 4400 along a line 4425. FIG.44D shows a zoomed-in view of a portion 4404 of the side-viewcross-section of FIG. 44C. FIG. 44E shows a zoomed-in view of a portion4406 of the side-view cross-section of FIG. 44C. The bolometer 4400includes a cap layer 4435

The bolometer 4400 includes a cap layer 4435 (e.g., a poly cap), a metallayer 4440 (e.g., titanium), a dielectric layer 4445 (e.g., Si₃N₄), adielectric layer 4460, a dielectric layer 4461, a dielectric layer 4462,a resistive layer 4450 (e.g., VOx), a leg metal layer 4455 (e.g.,titanium), a dielectric layer 4465 (e.g., Si₃N₄), and a dielectric layer4470 (e.g., VOx cap formed of SiO₂). In an aspect, the dielectric layers4460, 4461, 4462, and 4460 may be a thin dielectric layer, such as athin layer of Si₃N₄. The contact 4415 includes a basket liner layer4480. The contact 4420 includes a basket liner layer 4490.

At the portion 4404 of the bridge 4405, the cross-sectional views ofFIGS. 44C and 44D show that the metal layer 4440 is disposed on the caplayer 4435. The dielectric layer 4445 is disposed on the metal layer4440. The dielectric layer 4461 is disposed on the dielectric layer4445. The dielectric layer 4462 is disposed on the dielectric layer4461. The resistive layer 4450 is disposed on the dielectric layer 4462.The dielectric layer 4470 is disposed on the resistive layer 4450. Thedielectric layer 4465 is disposed on the dielectric layer 4470 and thedielectric layer 4462. The dielectric layer 4460 is disposed on thedielectric layer 4465.

At the portion 4406 of the vertical leg 4410, the cross-sectional viewsof FIGS. 44C and 44E (and also FIG. 45F further described below) showthe dielectric layer 4462 is disposed on the dielectric layer 4461. Theleg metal layer 4455 is disposed on the dielectric layer 4462 and issurrounded on at least two opposite sides by the dielectric layers 4460and 4462. The vertical leg 4410 has a tail 4464 of the dielectric layer4461. A gap 4492 is between the tail 4464 and a side of the dielectriclayer 4462, such that the tail 4464 faces the dielectric layer 4462. Insome aspects, as shown for example in FIGS. 44A and 44B, a ridge or stepmay be formed in the dielectric layer 4460 that is formed from anattachment of the leg 4410 to the bridge 4405 which adds structuralsupport to the bridge 4405. In this regard, various steps may beincluded in the bridge 4405 to improve structural integrity of thebridge 4405.

As shown for example in FIG. 44E, the vertical leg 4410 has a s-shaped(e.g., also considered z-shaped or serpentine-shaped) cross sectionformed of the leg metal layer 4455 surrounded by (e.g., passivated by)the dielectric layers 4460 and 4462, with the tail 4464 forming aresidual tab of the dielectric layer 4461. In this regard, the verticalleg 4410 has a bottom horizontal segment 4468, a top horizontal segment4469, and a middle vertical segment 4466 between (e.g., adjacent to) thebottom horizontal segment 4468 and the top horizontal segment 4469 thatcollectively define the s-shaped cross section. The bottom horizontalsegment 4468 is substantially perpendicular to the middle verticalsegment 4466 and substantially parallel to the top horizontal segment4469. The top horizontal segment 4469 is substantially perpendicular tothe middle vertical segment 4466. In some aspects, two segments/portionsmay be referred to as being substantially perpendicular if an anglebetween the segments/portions is within ±10° of 90°. In some aspects,two segments/portions may be referred to as being substantially parallelif an angle between the segments/portions is within ±10° of 0°.

The dielectric layer 4460 is formed on a first sidewall of the leg metallayer 4455 and a first side of the leg metal layer 4455. The dielectriclayer 4462 is formed on a second sidewall of the leg metal layer 4455and a second side of the leg metal layer 4455. The first sidewall isopposite the second sidewall and the first side is opposite the secondside. The first sidewall is substantially perpendicular to the firstside. The second sidewall is substantially perpendicular to the secondside. The vertical leg 4406 (e.g., each of its segments) has a firstdimension that extends in a first direction that is substantiallyperpendicular to a plane defined by a surface of a substrate (e.g., thesubstrate 4101) and a second dimension that extends in a seconddirection that is substantially parallel to the plane. In some aspects,as shown at least in FIGS. 44C and 44E, in the middle vertical segment4466, the first dimension (e.g., dimension along the z-direction) of thevertical leg 4406 is greater than the second dimension (e.g., dimensionalong the x- or y-direction) of the vertical leg 4406. In this regard,in the middle vertical segment 4465, the first dimension of the legmetal layer 4455 is greater than the second dimension of the leg metallayer 4455, the first dimension of the dielectric layer 4460 is greaterthan the second dimension of the dielectric layer 4460, and the firstdimension of the dielectric layer 4462 is greater than the seconddimension of the dielectric layer 4462. In the bottom horizontal segment4468 and the top horizontal segment 4469, the first dimension of thevertical leg 4406 is less than the second dimension of the vertical leg4406. In this regard, the first dimension of the leg metal layer 4455,the dielectric layer 4460, and the dielectric layer 4462 is less thanthe second dimension of the leg metal layer 4455, the dielectric layer4460, and the dielectric layer 4462, respectively.

FIGS. 45A through 45F illustrate cross-sectional side views associatedwith an example process for forming the bolometer 4400 in accordancewith an embodiment. FIGS. 46A through 46F illustrate top-viewsassociated with the example process in accordance with an embodiment.The cross-sectional side-views are along the line 4425 of FIG. 44A. InFIG. 45A, a release layer 4505 (e.g., polyimide) is deposited (e.g., ona substrate (not shown in FIG. 45A)). The cap layer 4435 is deposited onthe release layer 4505, the metal layer 4440 is deposited on the caplayer 4435, and the dielectric layer 4445 is deposited on the metallayer 4440. In FIGS. 45B and 46A, the dielectric layer 4461 is disposed(e.g., using thin sheet film deposition). A metal layer 4542 (e.g., asacrificial metal layer) is disposed on the dielectric layer 4461 andetched. In FIGS. 45C and 46B, the dielectric layer 4462 is disposed(e.g., using thin sheet film deposition) on the dielectric layer 4461and the metal layer 4542. The resistive layer 4450 is deposited on thedielectric layer 4462 and patterned/etched. The dielectric layer 4470 isdisposed on the resistive layer 4450. A zoom-in view of portions 4502and 4504 of FIG. 45C is shown in FIGS. 47A and 47B.

In FIG. 46C, trenches 4615 and 4620 to be utilized to form the contacts4415 and 4420, respectively, are formed. A metal layer 4605 is depositedand then etched away from a portion that is to form the bridge 4405 ofthe bolometer 4400. In FIGS. 45D and 46D, the basket liner layers 4480and 4490 are disposed, and the dielectric layer 4465 is deposited andetched. A basket is patterned and portions 4620 and 4625 are etched. toform contacts for the resistive layer 4450. In FIGS. 45E and 46E, theleg metal layer 4455 is deposited and partially etched off. In thisregard, a portion of the leg metal layer 4455 remains on the portions4620 and 4625 of the resistive layer 4450. The leg metal layer 4455 isdisposed on the basket liner layers 4480 and 4490. In FIGS. 45F and 46F,the dielectric layer 4460 is deposited, the leg metal layer 4455 is cutto form the vertical legs 4408 and 4410, the metal layer 4542 isremoved, and the release layer 4505 is removed to release the bridge4405 and the vertical legs 4408 and 4410. It is noted that FIG. 45Fshows a portion of the same cross-sectional side view of FIG. 44C. It isfurther noted that FIG. 46F shows the same perspective view as FIG. 44A.

In some embodiments, bolometers may have perforations defined throughportions of the bolometers that do not contain a resistive layer (e.g.,VOx). In some aspects, the perforations defined through a bolometer arealong a same plane/layer as the legs and bridge of the bolometer. Theperforations may be appropriately sized to reduce thermal massassociated with the bolometers while maintaining the bolometers'infrared sensing capabilities and structural integrity. In this regard,the perforations reduce thermal mass while allowing the bolometers tocapture incoming photons having a wavelength component within a desiredwavelength range. The reduced thermal mass for faster cooling and fasterheating of the bolometers. In some aspects, such bolometers may includevertical legs as described herein for connecting the bridges of thebolometers with the readout circuit (e.g., ROIC). In other aspects, suchbolometers do not utilize vertical legs to connect the bridges of thebolometers with the readout circuit.

FIG. 48 is a flowchart of illustrative operations that may be performedfor forming a bolometer according to an embodiment. In some embodiments,the bolometer may be any one of the bolometers described with respectto, for example, FIGS. 29, 32, 34, 36N, 37, 39D, 40, 41T, 42, 43A, 43B,and 44A-44E. By way of non-limiting example, the flowchart is describedwith respect to one or more of FIGS. 41A through 41T.

At block 4805, a bridge structure is formed on a sacrificial layer. Forexample, with reference to FIGS. 41S and 41T, the bridge structure mayinclude the bridge 4153 and the sacrificial layer may include therelease layer 4106. The bridge 4153 includes the protection layer 4108,the metal layer 4112 (e.g., metal absorber layer), the dielectric layer4114, the dielectric layer 4118 (e.g., thin film oxide layer), thedielectric layer 4122 (e.g., thin film oxide layer), the resistive layer4124, and the dielectric layer 4150 (e.g., thin film layer). In someportions of the bridge 4153, the leg metal layer 4146 is disposed on theresistive layer 4124 (e.g., to facilitate coupling of the bridge 4153 tothe substrate 4101 via the legs 4160). In some portions of the bridge4154, a cap layer (e.g., VOx cap) is disposed on the resistive layer4124.

At block 4810, an opening is formed in the sacrificial layer. Forexample, with reference to FIG. 41I, the opening may be the trench 4132.At block 4815, a contact metal layer is disposed on sidewalls of theopening. For example, with reference to FIGS. 41J through 41N, thecontact metal layer may be the contact metal layer 4134. As shown inFIGS. 41J through 41N, a layer of contact metal material may bedeposited and appropriately etched.

At block 4820, a leg structure is formed. The leg structure couples thebridge structure to the contact metal layer. For example, with referenceto FIG. 41T, the leg structure may include the leg 4160 that couples thebridge 4153 to the contact metal layer 4134. The leg 4160 includes thedielectric layer 4118, the dielectric layer 4122, the leg metal layer4146, and the dielectric layer 4150. Different portions of the leg 4160may have a z-shaped cross section (e.g., right-most portion of the leg4160 in FIG. 41T) or an s-shaped cross section (e.g., portionimmediately to the left of the right-most portion of the leg 4160 inFIG. 41T). The leg 4160 has tails 4154, 4156, and 4158 and the gaps4162, 4164, and 4166, respectively, above the tails 4154, 4156, and4158.

At block 4825, the sacrificial layer is removed to release the bridgestructure and the leg structure. After removal of the sacrificial layer,the bridge structure and the leg structure are suspended above thesubstrate 4101.

It is noted that the flowchart of FIG. 48 illustrates formation of onebolometer. In some cases, one or more additional bolometers may beformed (e.g., formed concurrently) with the formation of the onebolometer. For example, multiple bridge structures may be formed on thesacrificial layer at block 4805, multiple openings may be formed in thesacrificial layers at block 4810, and so forth.

FIG. 49 illustrates a perspective view of a bolometer 4900 in accordancewith an embodiment. FIG. 50 illustrates a top view of the bolometer 4900in accordance with an embodiment. The dielectric layer 4906 may be athin film layer formed of Si₃N₄. The bolometer 4900 includes a bridge4905, vertical legs 4908 and 4910, and contacts 4915 and 4920. Thebridge 4905 includes a sensing portion 4906 and a remaining portion 4907(e.g., also referred to as anon-sensing portion). The sensing portion4906 is a portion of the bridge 4905 that includes a resistive layer(e.g., VOx layer). The remaining portion 4907 is a portion of the bridge4805 that does not include the resistive layer. The remaining portion4907 surrounds the sensing portion 4906. The remaining portion 4907 hasperforations defined herein, of which a perforation 4909 is labeled. Thevertical leg 4908 connects to the sensing portion 4906 of the bridge4905 via a leg/bridge contact 5014. The vertical leg 4910 connects tothe sensing portion 4906 of the bridge 4905 via a leg/bridge contact5013. The contact 4915 includes a basket liner layer 4980. The contact4920 includes a basket liner layer 4990.

FIGS. 51A through 51C illustrate additional examples of bolometers inaccordance with one or more embodiments. In particular, FIGS. 51A, 51B,and 51C illustrate a top view of a bolometer 5100, 5130, and 5160,respectively. The bolometer 5100 of FIG. 51A includes a bridge 5105 witha sensing portion 5106 and a non-sensing portion 5107, vertical legs5108 and 5110, leg/bridge contacts 5113 and 5114, and contacts 5115 and5120. The non-sensing portion 5107 includes perforations, of which aperforation 5109 is labeled. The bolometer 5130 of FIG. 51B includes abridge 5135 with a sensing portion 5136 and anon-sensing portion 5137,vertical legs 5138 and 5140, leg/bridge contacts 5143 and 5144, andcontacts 5145 and 5150. The non-sensing portion 5137 includesperforations, of which a perforation 5139 is labeled. The bolometer 5160of FIG. 51C includes a bridge 5165 with a sensing portion 5166 andanon-sensing portion 5167, vertical legs 5168 and 5170, leg/bridgecontacts 5173 and 5174, and contacts 5175 and 5170. The non-sensingportion 5167 includes perforations, of which a perforation 5169 islabeled.

As shown in FIGS. 50 and 51A-51C, bolometers may have structuralcharacteristics that may be varied to obtain desired performance. Asnon-limiting examples, such structural characteristics include a numberof bends in a leg (e.g., a vertical leg), dimensions of a leg, materialsutilized to form the leg, a number of perforations in anon-sensingportion of a bridge, and an arrangement of the perforations.

FIG. 52 illustrates a cross-sectional side view of a portion of abolometer in accordance with an embodiment. The bolometer includes abridge 5205 and a leg 5210 coupled to the bridge 5205. The bridge 5205includes a sensing portion 5206 having a thermistor, and a non-sensingportion 5207 that does not have a thermistor (e.g., VOx). FIG. 53illustrates a cross-sectional side view of a portion of a bolometerhaving perforations defined therein in accordance with an embodiment.The bolometer includes a bridge 5305 and a leg 5310 coupled to thebridge 5305. The bridge 5305 includes a sensing portion 5306 having athermistor, and anon-sensing portion 5307 that does not have athermistor. The thermistor may be disposed on a first insulator. Asecond insulator may be disposed on the thermistor. An absorber layermay be disposed on the second insulator. A third insulator may bedisposed on the metal layer. Each of the first insulator, secondinsulator, or third insulator may include one or more insulator layers.Alternatively or in addition to the absorber layer shown in FIG. 53, anabsorber layer may be disposed between insulator layers of the firstinsulator.

Perforations 5309 and 5311 are formed in the non-sensing portion 5307.The perforations 5309 and 5311 may be formed using one or more etchingoperations. In some aspects, each etching operation may be implementedusing a different etch chemistry (e.g., dependent on the material to beetched). In some embodiments, the bolometer of FIG. 52 may haveperforations formed in the non-sensing portion 5207 to arrive at thebolometer of FIG. 53. In one case, each layer of material may be formedsuch that the layer has perforations defined therein. For example, afirst layer of material may be formed with perforations defined therein.A second layer of material may then be formed on the first layer ofmaterial, where the second layer of material has perforations definedtherein that align appropriately with the perforations of the firstlayer of material. In another case, the bolometer of FIG. 52 may beformed and then perforations formed through all the insulators of thenon-sensing portion 5207.

FIG. 54 is a flowchart of illustrative operations that may be performedfor forming a bolometer having perforations defined therein according toan embodiment. In some embodiments, the bolometer may be any one of thebolometers described with respect to, for example, FIG. 49, 51A-51C, and53.

At block 5405, a bridge structure is formed. In some embodiments, thebridge structure may be formed by performing operations similar to thoseprovided in FIG. 25. In some cases, some or all of the blocks shown inFIG. 25 may be performed to form a bridge structure.

At block 5410, legs for connecting the bridge structure to a readoutcircuit are formed. In some aspects, the legs are vertical legs asdescribed with reference to one or more embodiments. In some cases, thevertical legs may be formed as the bridge structure is formed. In someembodiments, the legs may be formed by performing operations similar tothose provided in one or more of FIGS. 20-22.

At block 5415, perforations are formed in the bridge structure to obtaina microbolometer bridge. The perforations may be formed using one ormore etching operations. In some aspects, each etching operation may beimplemented using a different etch chemistry (e.g., dependent on thematerial to be etched). Alternatively, perforations may be formed witheach layer. In this case, semiconductor processing techniques areperformed to directly form the microbolometer bridge (e.g., without needto form a bridge structure in its entirety without the perforations andthen form perforations in the bridge structure). For example, a firstlayer of material may be formed with perforations defined therein. Asecond layer of material may then be formed on the first layer ofmaterial, where the second layer of material has perforations definedtherein that align with the perforations of the first layer of materialas appropriate.

Note that one or more operations of FIG. 54 may be combined, omitted,and/or performed in a different order as desired. For example, thebridge structure, the legs, and/or the perforations in the bridgestructure may be formed together and/or as separate processing steps.

FIGS. 55A through 55D illustrate cross-sectional side views associatedwith an example process for forming a bolometer in accordance with anembodiment. FIG. 56 illustrates a top-down view corresponding to thecross-sectional side view of FIG. 55D in accordance with an embodiment.Various features of FIGS. 55A through 55D may be implemented in the sameor similar manner as corresponding features of FIGS. 36A-36N and/orother figures.

In FIG. 55A, the structure includes a substrate, an overglass layer5602, pads 5604, a release layer 5506, a protection layer 5508, a metallayer 5512, a dielectric layer 5514 (e.g., Si₃N₄/SiO₂), a metal layer5520, a resistive layer 5524 (e.g., VOx layer), a dielectric layer 5526,a contact metal layer 5534, and a leg metal layer 5546. The structurealso includes other layers (e.g., dielectric layers) similar to those inFIGS. 36A-36N but not explicitly labeled in FIG. 55A. In FIG. 55B,patterning and etching operations are performed on the structure of FIG.55A. In FIG. 55C, patterning and etching operations are performed on thestructure of FIG. 55B to define perforations in a bolometer bridge(e.g., a non-sensing portion of the bolometer bridge). One exampleperforation 5550 is shown in FIGS. 55C, 55D, and 56. In FIG. 55D and 56,operations are performed on the structure of FIG. 55C. Such operationsremove the release layer and form tails of dielectric layers. It isnoted that perforations, including the perforation 5550, is shown ashaving an octogonal shape. More generally, perforations may be of othershapes, such as other polygonal shapes (e.g., rectangular shaped),circular shapes, and/or others. Each of FIGS. 55A-55D may becross-sectional side views taken along a line 5605 shown in FIG. 56.

Thus, bolometers are provided in accordance with various embodiments.Using various embodiments, bolometers having various characteristics maybe formed as appropriate dependent on application. Various examplecharacteristics are provided as follows. Pixels (e.g., bolometers andassociated legs) have appropriate material and structure to provide aflat bolometer (e.g., a flat bridge). A flatter bolometer is better ableto avoid deflection (e.g., relative to an initial plane) due to materialstresses, avoid stray light, and so forth. An example figure of meritfor bolometers may be based on a noise equivalent temperature differenceand a thermal time constant. In an aspect, the figure of merit isdesired to be low. To achieve a low figure of merit, a thin bridge and alow thermal time constant is desired. In some cases, the figure of meritis proportional to the bridge's thermal mass and independent of a legthermal conductance.

It is noted that the foregoing describes microbolometers with absorberlayers. One or more absorber layers may be provided above a resistivelayer, and/or one or more absorber layers may be provided below aresistive layer. An absorber layer may be in contact with a resistivelayer, or one or more dielectric layers may intervene between theabsorber layer and the resistive layer. In some cases, an enhancinglayer may be in contact with an absorber layer. The enhancing layer andthe absorber layer may provide enhanced infrared absorption for themicrobolometers. By way of non-limiting examples, an enhancing layer maybe formed from titanium, titanium oxide, a combination of Ti and TiOx,aluminum, titanium nitride, nickel, iron, zinc, platinum, tantalum,chrome, other transition metals, other metals, alloys of these metals,oxides of these materials, and/or a combination of these metals andtheir oxides. Examples of microbolometers with absorber layers and/orenhancing layers can be found in U.S. Pat. No. 9,945,729, which isincorporated herein by reference in its entirety.

It is noted that dimensional aspects provided above are examples andthat other values for the dimensions can be utilized in accordance withone or more implementations. Furthermore, the dimensional aspectsprovided above are generally nominal values. As would be appreciated bya person skilled in the art, each dimensional aspect has a toleranceassociated with the dimensional aspect. Similarly, aspects related todistances between features provided above are also examples and alsohave associated tolerances. It is also noted that although the foregoingdescribes forming of perforations using etching operations, othersemiconductor processing techniques appropriate to remove material, suchas drilling operations, laser operations, may be performed to form theperforations, as would be understood by one skilled in the art.

Where applicable, various embodiments of the invention may beimplemented using hardware, software, or various combinations ofhardware and software. Where applicable, various hardware componentsand/or software components set forth herein may be combined intocomposite components comprising software, hardware, and/or both withoutdeparting from the scope and functionality of the invention. Whereapplicable, various hardware components and/or software components setforth herein may be separated into subcomponents having software,hardware, and/or both without departing from the scope and functionalityof the invention. Where applicable, it is contemplated that softwarecomponents may be implemented as hardware components and vice-versa.

Software, in accordance with the invention, such as program code and/ordata, may be stored on one or more computer readable mediums. It is alsocontemplated that software identified herein may be implemented usingone or more general purpose or specific purpose computers and/orcomputer systems, networked and/or otherwise. Where applicable, orderingof various steps described herein may be changed, combined intocomposite steps, and/or separated into sub-steps to provide featuresdescribed herein.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. An infrared imaging device comprising: a microbolometer arraycomprising a plurality of microbolometers, wherein each microbolometercomprises: a microbolometer bridge comprising: a first portioncomprising a resistive layer configured to capture infrared radiation;and a second portion having a plurality of perforations defined therein.2. The infrared imaging device of claim 1, wherein the first portionfurther comprises a first insulator and a second insulator, wherein theresistive layer is disposed on the first insulator, and wherein thesecond insulator is disposed on the resistive layer.
 3. The infraredimaging device of claim 2, wherein the first portion further comprisesan absorber layer disposed on the second insulator.
 4. The infraredimaging device of claim 3, wherein the first portion further comprises athird insulator disposed on the absorber layer.
 5. The infrared imagingdevice of claim 2, wherein the first portion further comprises anabsorber layer, wherein the first insulator is disposed on the absorberlayer, and no portion of the resistive layer is in the second portion.6. The infrared imaging device of claim 1, further comprising asubstrate comprising a plurality of contacts and a surface, wherein thesurface defines a plane, wherein each microbolometer further comprises aleg structure coupled to the microbolometer bridge and to one of theplurality of contacts, and wherein the leg structure comprises across-section having a first section, a second section substantiallyparallel to the first section, and a third section joining the firstsection and the second section.
 7. The infrared imaging device of claim6, wherein the third section is substantially perpendicular to the firstand second sections, wherein the first portion is a sensing portion ofthe microbolometer bridge, and wherein the second portion isanon-sensing portion of the microbolometer bridge.
 8. The infraredimaging device of claim 6, wherein the third section is at an anglerelative to the first and second sections, wherein the leg structureextends between the microbolometer bridge and the one of the pluralityof contacts in a first direction substantially parallel to the plane,and wherein the microbolometer bridge, the leg structure, and theperforations are along a common plane.
 9. The infrared imaging device ofclaim 8, wherein: the cross-section is an s-shaped cross-section or az-shaped cross-section maintained along the first direction, the firstsection and the second section extend along the first direction and asecond direction substantially parallel to the plane, and the thirdsection joins the first section and the second section in a thirddirection that is substantially perpendicular to the plane.
 10. Theinfrared imaging device of claim 6, wherein the leg structure comprises:a first segment associated with the first section and having a firstdimension that extends in a first direction that is substantiallyparallel to the plane and a second dimension that extends in a seconddirection that is substantially perpendicular to the plane, wherein thefirst dimension is greater than the second dimension; a second segmentassociated with the second section; and a third segment associated withthe third section and adjacent to the first segment and the secondsegment, the third segment having a third dimension that extends in thefirst direction and a fourth dimension that extends in the seconddirection, wherein the third dimension is less than the fourthdimension.
 11. The infrared imaging device of claim 10, wherein: each ofthe first segment, the second segment, and the third segment comprises arespective portion of a first metal layer, a respective portion of afirst layer, and a respective portion of a second layer, the first layeris formed on a first sidewall of the first metal layer and a first sideof the first metal layer, the second layer is formed on a secondsidewall of the first metal layer and a second side of the first metallayer, the first sidewall is opposite the second sidewall, and the firstside is opposite the second side.
 12. The infrared imaging device ofclaim 11, wherein a portion of the first layer and a portion of thesecond layer are separated by a gap, and wherein the portion of thefirst layer faces the portion of the second layer.
 13. The infraredimaging device of claim 6, wherein the first portion further comprises:a cap layer facing the substrate; a first metal layer disposed on thecap layer; a first dielectric layer disposed between the first metallayer and the resistive layer; a second dielectric layer disposed on theresistive layer; and a third dielectric layer disposed on the seconddielectric layer, wherein the leg structure is in contact with the thirddielectric layer.
 14. The infrared imaging device of claim 13, whereinthe first portion further comprises: a second metal layer disposed onthe third dielectric layer; and a fourth dielectric layer disposed onthe second metal layer.
 15. The infrared imaging device of claim 6,wherein the first portion further comprises: a cap layer facing thesubstrate; a first dielectric layer disposed on the cap layer; a seconddielectric layer, wherein the resistive layer is disposed between thefirst dielectric layer and the second dielectric layer; a metal layerdisposed on the second dielectric layer; and a third dielectric layerdisposed on the metal layer, wherein the leg structure is in contactwith the third dielectric layer.
 16. A method of forming the infraredimaging device of claim 7, the method comprising: forming a bridgestructure; forming the leg structure; and forming the plurality ofperforations in the bridge structure to obtain the microbolometerbridge.
 17. A method of forming an infrared imaging device, the methodcomprising: forming a bridge on a sacrificial layer, wherein the bridgecomprises: a first portion comprising a resistive layer configured tocapture infrared radiation; and a second portion having a plurality ofperforations formed therein; forming an opening in the sacrificiallayer; disposing a contact metal layer on sidewalls of the opening;forming a leg structure that couples to the bridge and the contact metallayer; and removing the sacrificial layer to suspend the bridge and theleg structure above a substrate of the infrared imaging device, whereinthe contact metal layer is coupled to the substrate.
 18. The method ofclaim 17, wherein the forming the bridge comprises: disposing a firstdielectric layer on a cap layer; disposing the resistive layer on thefirst dielectric layer; disposing a set of dielectric layers on theresistive layer; disposing a second metal layer on the set of dielectriclayers; and disposing a second dielectric layer on the second metallayer, wherein the leg structure comprises a cross-section having afirst section, a second section substantially parallel to the firstsection, and a third section joining the first section and the secondsection.
 19. The method of claim 18, wherein the forming the bridgefurther comprises: etching through a portion of the cap layer, a portionof the first dielectric layer, a portion of each dielectric layer of theset of dielectric layers, a portion of the second metal layer, and aportion of the second dielectric layer to define the plurality ofperforations.
 20. The method of claim 17, wherein the forming the bridgecomprises: disposing a second metal layer on a cap layer; disposing afirst set of dielectric layers on the second metal layer; disposing theresistive layer on the first set of dielectric layers; disposing asecond set of dielectric layers on the resistive layer; and etchingthrough a portion of the cap layer, a portion of the second metal layer,a portion of each dielectric layer of the first set of dielectriclayers, and a portion of each dielectric layer of the second set ofdielectric layers to define the plurality of perforations.